Mysterious Abandoned Building by Zell23

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.​

2d game, 2dcg, animated, bestiality, big ass, big tits, combat, fantasy, female domination, japanese game, lactation, male protagonist, mind control, monster girl, oral sex, rape, teasing, titfuck, vaginal sex

1. Extract and run.

Demo v1.27
[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
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.

[operations]
Move: ⇄key
Alter ego: A key
Masturbation: S key
Move floor/Examine:↑Key
[Other operations]
Camera scaling: 4.5 keys