Complete Other Mysterious Abandoned Building [v1.80] [Zell23]

OnlyFriend · 2026-06-22T01:02:56-0700

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Overview:
The game takes place inside a decaying, multi-floor abandoned building filled with dark corridors, strange rooms, and hostile creatures. The focus is on slow exploration, environmental tension, and navigating the building’s floors while encountering enemies and scripted events. Each update typically introduces new rooms, enemy animations, or mechanics, and reflects the author's iterative development style. Unlike his more combat-focused projects, Nazo no Haibiru leans into a claustrophobic horror tone, highlighting tight spaces, surprise encounters, and survival-style progression. Players must explore carefully, pay attention to environmental clues, and avoid or endure encounters with the building’s residents.

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Extract and run

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IMPORTANT NOTICE REGARDING FUTURE UPDATES
This current version is intended to be the final release. Due to the difficulties of publicly sharing adult (H-animation) content while co-developing the project, we have determined it is no longer feasible to continue updating this title.

VERSION 1.80 UPDATE DETAILS
New Content

New Enemy: Added a new "Unknown" enemy type: Sahagin.
New Scenes: Added adult (H) animation sequences for the Sahagin.
Location: The Sahagin hunts in damp, waterside areas.
Specific Event: This update includes a capture scene where the character Hop is caught by the Sahagin. Note: In this specific scenario, the player cannot save her.

Game Flow Changes

NEW GAME: Now starts with the full introductory sequence.

Demo Room System To facilitate viewing specific scenes, a central "Demo Room" has been added.

Navigation: Use the gates in the room to warp directly to specific H-event locations.
Emergency Return: If you get stuck or an event breaks:ç
B_ver: Press SPACE to return to the Demo Room.
A_ver: Press A to return to the Demo Room.

Warnings

Speed Toggle: You can still press 'S' to increase game speed. However, this may cause character position errors and prevent events from triggering correctly. Please use with caution.
Visual Effects: Some effects, such as cross-section diagrams, are currently experimental and may be changed or removed without notice.

Enemy Roster (B_ver) The following enemies are available in the demo:

Eater
Big Puppy
Melty Head
Humanoid
Harmful Bird (3 types)
Bad Trip
Statue
Lycanthrope
Sahagin (New)
?????? (Hidden)

[add]

・Added two H anime to the test map (Mizuhime, Squeezing Nest)

[amendment]

・Changed the avoidance motion to X→D key (and changed D's debug key to W)
・Some modifications to the monster dot map graphics

★Character introduction

[Mizuhime]
A monster that appears in the waterhole. It clings to your feet to squeeze out the milk that approaches you carelessly.

[Sperm-milling nest]
Monsters with powerful powers may be building webs and capturing prey. The way prey is managed differs depending on each monster, but the captive victim is no longer sane and cannot be saved.

Sometimes you need to hide in the forest in order to evade surveillance.

[add]

・Added two H animations to the test map( Red Hood Venomhayes )

[amendment]

・Some modifications to the monster dot map graphics
・Make the gallery easy to understand (may be heavy)

Since adjustments are being made around the HP system, strange behavior may occur

★Character introduction

[ Red food ]

A monster wearing crimson clothes all over its body. They don't speak the same language and will attack you if they find a human.

It's like I'm collecting something while wandering around in the ruins...

[ Venom haze ]

A monster that spews gas 〇〇 from its body. His face is covered with a gas mask, so it is impossible to see his expression. As you approach defenselessness, you will be in a 〇〇 state in no time...

[add]

・Added two H animations to the test map( Mimic Ghoul )

[amendment]
・Some modifications to the monster dot map graphics

★Character introduction

[ Mimic ]
A monster lurking inside a box.
When the protagonist approaches, he reaches out and tries to catch him.

[ Ghoul ]

It wanders around in ruins like a zombie.

[add]

H animation on the test map Two added ( Imp · Monitor head )

[amendment]

-Organize menu screens
・Some modifications to the monster dot map graphics

★Character introduction

[imp]
Lower devil. He appears as a servant of a high-ranking demon and attacks the protagonist.
Basically, the semen is expressed by the tail.

[monitor head]
A creepy monster with a mechanical head.
When it finds the main character, it not only chases after it, but also seems to have various abilities. .. ..? ( Demo not implemented

Vaginal live commentary

★Organize menu items

The menu has been renovated, and the equipment section has been divided into basic equipment and selective equipment.
Items that affect the main character's condition are summarized in selected equipment, and the tools section is necessary for solving puzzles
I'll just do it. Selective equipment can be attached and detached.