Much like the game Carrion or other monster-evolution titles, the protagonist must consume mana or biological matter to evolve into larger, more complex forms.
Protagonists often unlock specific abilities such as Tentacle Shield , Slime Clone , or advanced camouflage.
Certain adult-oriented versions, like I Became a Tentacle Monster that Corrupts Magical Girls , follow an unemployed man named Hakuto who accepts a deal with a mysterious gem. He gains dark powers and spends his time hunting and "managing" a harem of magical girls. Core Gameplay & Story Mechanics
Most of these "Game World" stories rely on standard Isekai tropes integrated with a leveling system: