Mumasekai: Lost in the World of Succubi (also known as Yume Ma Sekai no Mayoibito
) is a side-scrolling action-RPG and "Metroidvania" style game released on September 12, 2025, by developer Shimofumi-ya and publisher OTAKU Plan Story and Premise
The game follows a protagonist who awakens in a mysterious "Succubus World" accompanied by
, a character who has taken human form. To escape this dream realm and return to reality, the player must navigate dangerous environments like the Eternal Night Forest Succubi City to find the legendary Bell of Awakening Gameplay Features Combat and Skills
: The game features a classic side-scrolling combat system involving jumping, dodging, and attacking with a sword that can be upgraded with "Dream Metal" to gain abilities like Sharpness and Tornado Slash.
: Exploration is aided by acquiring various items and artifacts, such as the Salamander's Mark (allowing for flame attacks), a Treasure Detector Survival Mechanics
: Players have a stamina gauge that decreases when hit by enemy attacks or "temptations." If the gauge reaches zero while the character is restrained, it leads to a defeat scene. Multiple Endings : The game features two primary endings: Normal End : Achieved through standard completion. : Requires collecting five pieces of the Forget-Me-Not Flower
and using them during the final scene to reveal a secret about Kuro. Availability and Performance
Review for Lost in the World of Succubi - NEP - Steam Community
Mumasekai – Lost in the World of Succubi (夢魔世界の迷い人) is a 2D action-adventure Metroidvania developed by Shimofumi-ya and published by OTAKU Plan . Released on Steam in September 2025
, it follows a young boy and his cat, Kuro, who are drawn into a dream realm ruled by seductive succubi. Core Story & Setting
The game centers on a protagonist who awakens in the "Succubus World," a dangerous realm where monsters steal life force through dreams.
: After being captured by the Succubus Queen, the protagonist must explore five unique areas to find three keys, unlock the Queen's Palace, and ring the Bell of Awakening to return home. Atmosphere
: The world is built with detailed pixel art and a classic side-scrolling feel. Gameplay Mechanics
The title blends classic platforming with character progression.
: Initial moves include simple slashes, dodges, and jumps. Combat is described as intuitive and satisfying, featuring intense boss battles—such as a spider succubus—that serve as major gameplay highlights. Exploration (Metroidvania) : As you progress, you unlock critical abilities like Double Jump Underwater Breathing to access previously unreachable areas. Difficulty & QoL
Three difficulty levels (Easy, Normal, Hard) that can be swapped anytime. Fast travel between save points to minimize backtracking. Controller support and key remapping for smoother play. Content & Features Adult Content : The game features approximately 29 real-time H-scenes
using pixel-style chibi characters. Most are triggered by "defeat events," though players can also unlock them by defeating specific succubi. Progression
: A map filled with hidden treasure chests and gear that can be purchased with coins found during exploration. Multiple Endings
: There are two main endings, including a "True End" that unlocks additional animations in the gallery. Availability : Primarily available on Steam Store : Built on the Unity Engine
, it is marked as "Playable" on Steam Deck, though it may require some manual controller configuration. finding the hidden areas in maps 2 through 5 or more details on the True Ending requirements Lost in the World of Succubi on Steam
Feature: Surviving the Dreams of Mumasekai Mumasekai: Lost in the World of Succubi
is a 2D side-scrolling exploration RPG that challenges players to escape a surreal realm ruled by seductive demons. Combining Metroidvania-style exploration with tactical combat, the game emphasizes survival through agility and wit. 🕹️ Core Gameplay Mechanics
The game follows a classic progression where players must unlock the map by finding new gear.
Tactical Action: Combat relies on a simple yet satisfying three-button system: Jump, Dodge, and Slash.
Precision Countering: Timing a dodge perfectly triggers a slow-motion effect followed by a powerful counterattack.
Metroidvania Elements: Explore a vast, interconnected map filled with hidden treasure chests and secret areas.
Escalating Hazards: As the player deepens their exploration, the "temptation" from succubi enemies increases in intensity. 🗺️ World and Progression
Players take on the role of a protagonist who awakens in the Succubus World with no immediate way home.
Character Progression: Gain new skills and passive abilities to overcome increasingly difficult obstacles. mumasekai lost in the world of succubi new
Teleportation: Players can warp to Save Points at any time to minimize backtracking through previously cleared areas.
Multiple Endings: The story branches into two main paths: the Normal End and the True End, the latter of which requires specific collectibles to unlock.
Difficulty Scaling: Includes three difficulty levels that can be changed at any point during gameplay to suit your preferred challenge. 🛠️ Quality-of-Life Features
Designed for smooth playability, the game includes several modern conveniences:
Instant Retry: Get back into the action immediately after a defeat.
Event Skipping: Quickly bypass previously seen dialogue or cutscenes.
Destination Guidance: A visual display helps players find their next objective in the labyrinth.
Customizable Controls: Full gamepad support and key configuration options. 🔗 Useful Resources Latest News: Follow updates on the Official Steam Page.
Publisher Info: Check for more titles and announcements at OTAKU Plan. If you'd like to dive deeper, I can help you with:
Finding the Forget-Me-Not Flower locations for the True Ending Tips for defeating the Stage Bosses Troubleshooting Steam Deck compatibility settings Let me know which part of the game you'd like to focus on! Lost in the World of Succubi on Steam
Lost in the World of Succubi (also known as Mumasekai) is a 2D action-RPG Metroidvania developed by Shimofumi-ya. This guide covers the essential mechanics and steps to reach the game's completion, including the hidden True End. Core Gameplay Mechanics
Controls: The game uses simple, intuitive controls: Jump, Dodge, and Slash. Most versions also support Z for main attacks/magic and X for secondary/melee attacks.
Exploration: As a Metroidvania, the game features a large world map with hidden areas and treasure chests. You can unlock new weapons and gear to access previously unreachable sections.
Fast Travel: You can teleport to any discovered Save Point at any time, which significantly reduces backtracking.
Difficulty: You can change the game's difficulty at any time if you find certain bosses too challenging. Essential Walkthrough Tips VGH Let's Play - Lost in the World of Succubi (PC)
While specific plot details vary, most versions follow this structure:
The “New” version often adds more side quests, additional succubus characters, and refined adult scenes.
Score: 6/10
Pros:
Cons:
Final Word: Mumasekai: Lost in the World of Succubi is a competent, pretty, but ultimately safe release. It checks all the boxes but refuses to color outside the lines.
The game Lost in the World of Succubi (also known as Mumasekai), developed by Shimofumi-ya and published by OTAKU Plan , was released on Steam on September 12, 2025. This title is a side-scrolling, pixel-art Metroidvania where players take on the role of a protagonist who awakens in a mysterious realm inhabited by dangerous, alluring succubi. Gameplay and Mechanics
The game focuses on high-speed exploration and satisfying combat within a sprawling labyrinth.
Action-Packed Combat: Players navigate the world using a simple yet effective control scheme consisting of "Jump," "Dodge," and "Slash".
Metroidvania Progression: As you explore, you discover treasures, new weapons, and specialized gear that unlock previously inaccessible areas of the map.
User-Friendly Features: The developer included several quality-of-life options, such as the ability to change difficulty at any time, instant retries, and a fast-travel system available from anywhere on the map. Story and Endings
The narrative follows the protagonist's struggle to avoid the interference of succubi and find a way back to his original world. A key companion in this journey is a cat named Kuro. The game features two distinct conclusions:
Normal End: Reached by completing the game through standard progression.
True End: To unlock this secret ending, players must collect all 5 pieces of the Forget-Me-Not Flower before the final encounter. Choosing to use this item reveals a major plot twist: Kuro has the ability to transform into a human form in the real world. Performance and Availability Platform: Currently available on Steam . Mumasekai: Lost in the World of Succubi (also
Reception: The game maintains a "Positive" rating, with roughly 83% of players recommending the title as of late 2025.
Accessibility: It supports gamepads, customizable key configurations, and adjustable text speeds to accommodate different playstyles. Lost in the World of Succubi on Steam
Based on the title provided, this appears to refer to a specific entry in the adult-oriented visual novel or RPG genre, likely a translation or localization of a Japanese "doujin" (independent) game.
Here is an informative overview regarding the title "Mumasekai: Lost in the World of Succubi" (often associated with the New/Updated versions or the original Japanese title Mumasekai).
"Mumasekai: Lost in the World of Succubi" is an adventure role-playing game (RPG) developed by the Japanese circle Nanakusadou. It falls under the subgenre of "ero-RPG" or "H-RPG," combining traditional role-playing game mechanics with adult-themed storytelling.
The game is widely known for its distinct art style and a narrative centered around themes of enchantment, survival, and temptation.
Choose one:
Which option do you want?
Mumasekai: Lost in the World of Succubi (New)
Prologue: The Fracture
Kaito never believed in parallel worlds. He was a third-year university student, buried in data structures and caffeine, his biggest escape the pixelated battlefields of online games. That was until the night his screen didn’t just glitch—it yawned.
A notification popped up, not from any installed software: 「Mumasekai: Do you accept the New World? Y/N」
He scoffed and reached for ‘N’, but his finger slipped. The moment his skin brushed the ‘Y’, his chair dissolved. His room warped like wet paint dragged sideways. A sound like shattering glass pierced his skull, and then—nothing but warm, velvet darkness.
When he opened his eyes, he was lying on a bed of crushed rose petals, staring at a sky the color of a bruise, lit by three moons: one lavender, one magenta, one gold. The air smelled of honey, sweat, and something ancient. He sat up slowly, his clothes replaced by a thin, silken tunic that left little to the imagination.
“Welcome, lost lamb,” a voice purred from the shadows. A figure emerged—tall, with skin like polished obsidian and hair that moved like smoke. Her eyes were vertical slits of molten amber. She wore chains of opal that did nothing to obscure her form. “You’ve stumbled into Mumasekai. The New Revision. We’ve been waiting for a human soul.”
Kaito’s throat went dry. “Where… where am I?”
The succubus smiled, revealing teeth just a little too sharp. “You’re in the pleasure labyrinth, darling. And you are the only key.”
Chapter One: The Nature of the New World
Mumasekai was not the hell of fire and brimstone. It was a hell of want. A dimension crafted from the psychic residue of human desire, ruled not by demons with whips, but by the Succubi Council of Seven—each embodying a different facet of temptation: Lust, Glamour, Envy, Sloth, Vanity, Obsession, and Avarice.
But this was the new Mumasekai. The old version, Kaito learned, had grown stagnant. Succubi had grown bored feeding on the same repetitive dreams, the same tired fantasies. So they had evolved. The new rules were simple, yet terrifying:
Kaito was the first human to arrive in the new iteration. He was a novelty. A rare vintage.
Chapter Two: The First Temptation (Lust)
His first guide was the obsidian-skinned succubus named Lilura. She took him to the Boudoir of Echoes, a room where every surface reflected a different version of Kaito’s own deepest fantasies—not just sexual, but emotional. He saw himself as a celebrated artist, as a beloved husband, as a father. The images whispered to him.
“All you have to do,” Lilura breathed into his ear, her forked tongue tracing the curve of his cartilage, “is say ‘I give in.’ Just once. And you can live any of these lives. Forever.”
Kaito’s heart raced. His tunic felt suffocating. But something in him—stubborn, logical, terrified—clung to a fragment of his old self. “No,” he whispered. “These aren’t real. They’re stolen from my head.”
Lilura’s smile faltered. For a moment, something almost like respect flickered in her amber eyes. “Interesting. The new ones usually break in the first hour.”
She snapped her fingers, and the room dissolved. Kaito found himself in a corridor of black mirrors.
Chapter Three: Glamour and the Mask
The second trial was Mira, the Succubus of Glamour. She appeared as everything Kaito had ever wished to be: taller, stronger, more handsome, with a voice like warm whiskey. She offered him a mask. Protagonist : A human (often male, but some
“Put it on,” she said, holding a porcelain face that smiled with his own lips. “Wear it for one day. You’ll be adored. Admired. You’ll never feel insecure again.”
Kaito looked at the mask. He remembered every cruel comment, every awkward silence, every moment he’d wished to be someone else. His hand reached out.
Then he stopped. “If I wear this,” he said slowly, “who will remember who I really am? Will I even care?”
Mira’s perfect face cracked—literally, a hairline fracture down her cheek. “You’re no fun,” she pouted, and vanished into a cloud of shimmering dust.
Chapter Four: The Descent
But Mumasekai did not give up easily. It adapted. The trials grew more insidious.
By the sixth trial—Obsession (Succubus Fixa) —Kaito was hollow. Fixa didn’t tempt him with pleasure or power. She gave him a puzzle: a single, unsolvable riddle about a woman he’d once loved from afar. “Spend eternity solving it,” she cooed. “Never let go.”
For three days (or three centuries—time had no meaning), Kaito stared at the riddle. He nearly lost himself in the beautiful torture of it. But finally, he looked up and said, “I choose to forget her.”
Fixa screamed and dissolved into a swarm of moths.
Chapter Five: The Seventh (Avarice)
The final succubus was Mammona, the Succubus of Avarice. She did not appear beautiful. She appeared as a withered old woman in a counting house, surrounded by floating coins made of solidified tears.
“You’ve refused six gifts,” Mammona said, her voice like rusted gears. “But the seventh is different. I don’t offer pleasure. I offer power. The power to reshape Mumasekai itself. You could become a king here. A god. You could go home and take this world with you—control every desire of every human you meet.”
She placed a single golden coin on his palm. It was warm. Alive.
Kaito looked at the coin. He thought about his cramped apartment, his student loans, his lonely weekends. He thought about the power to never be ignored again.
His fingers closed around the coin.
Mammona’s eyes glittered. “Say it.”
Kaito’s jaw tightened. He remembered Lilura’s words: consent cannot be forced. He remembered every trial, every near-fall. He wasn’t the same person who had slipped on a keyboard.
He opened his hand. The coin dropped.
“I don’t want to be a god,” he said. “I just want to go home and be a decent human.”
Epilogue: The Return
The Seventh Gate opened not with a roar, but with a sigh. It was a simple wooden door, the kind from his childhood home. Kaito walked through.
He woke up in his chair, face-down on his keyboard. The screen showed a blinking cursor. His clock read 11:59 PM—the same second he’d left. The only evidence of his journey was a single crushed rose petal on his desk, and a faint, warm scar on his left palm where the golden coin had rested.
He never told anyone what happened. But sometimes, late at night, when the world felt too heavy, he would hear a distant, playful whisper on the wind: “Come back, Kaito. The New World is always changing. We’ve already released an update.”
He would smile, close the window, and lock the door.
But he never deleted the notification.
It still waits there. Unanswered.
Y/N?
Mumasekai – Lost in the World of Succubi is a 2D Metroidvania by Shimofumi-ya focused on exploration, responsive platforming, and strategic skill usage. Players must navigate a labyrinth, collect items to achieve the "True End," and master the dash-roll for survival. For more details, visit Steam Community. Lost in the World of Succubi on Steam
Title: Mumasekai: Lost in the World of Succubi Platform: PC (Steam) Genre: RPG / Adventure / Nudity Developer: Dieselmine Release Date: April 2024
A frequent criticism of the original was the lack of male rivals or allies. Mumasekai New introduces three other “lost” humans—each with unique survival strategies. One, a cynical ex-priest, is immune to seduction but slowly loses his empathy. Another, a teenage athlete, becomes dangerously addicted to succubus essence. These characters can be saved, betrayed, or romanced (in a tragic, human-tragic way).
This is the primary reason most players will buy the game, and in this regard, it delivers exactly what is promised.