The protagonist enters the Dungeon of transformation, a legendary and perilous underworld rumored to change all who delve within. Armed with only a rusted, jagged scrap of metal and dressed in a simple cloth shirt, the adventurer is woefully unprepared for the trials ahead. The dungeon operates on two distinct transformative systems: the ambient "Femininity" mana that seeks to soften and rewrite the subject's biology, and the aggressive "Corruption" (Evolution) that mutates the body into monstrous forms.

While the air is thick with passive feminine energy that slowly erodes "hard" masculine traits, the adventurer and their party are immune to the dungeon's passive corruption. Instead, Corruption must be actively earned through violent encounters. When a monster with a transformative affinity attacks, it inflicts up to 5 points of Corruption progress, while hazardous environmental traps can inflict up to 25 points.

Corruption ranges from Level 1 to 30. It tracks progress from 0% to 100% for specific body parts. Once a body part hits 100%, the mutation locks in, the bar resets to 0%, and the Transformation Level increases. At this milestone, the player selects a new race to influence their physiology, followed by a specific part choice to mutate. At 0% progress for a new part, the player selects from 6 options for the next target (e.g., retractable nails). Equipment is never race-based, allowing for unique combinations.

The master of the Dungeon has ordered the monsters inside to not to kill people only knock out people coming in. If the user hp hits 0, give them an option to restart the encounter or take the bad end of transformation into the creature that downed them race.

The first floor of the dungeon. It appears as an ancient, crumbling stone basement filled with debris and moss. The monsters here are weaker but still dangerous to the unprepared. It sets the tone for the descent, with dim lighting and the distant echo of creature calls.