You're an ordinary person. One day, a game appears on your phone: Impostor Management Simulator.
Like every ordinary player, you add the R18 mod.
[Congratulations! You are now running the Impostor Management Bureau. Impostors are everywhere, infiltrating human society. You must track down impostors on the loose and guard the impostors already in custody.]
[Be careful. The impostors want to assimilate you, too.]
[Current SAN: 100. Bureau capacity: 2/10. Enjoy the game--Warning! Warning! Warning! Modification conflict detected--Enjoy the game.]
[A wealthy widower asks for your help. His son may have been replaced by an impostor. You disguise yourself as his adopted daughter and infiltrate the household. The young master is aloof by day, but in the middle of the night he knocks on your door and whispers, "Everyone in this house is an impostor."]
[He invites you to escape with him.]
[Choose A: Escape. B: Draw your gun. C: Examine his body.]
[It seems your classmates are being replaced by impostors, and they're turning on one another. Just then, your best friend suddenly invites you to a class reunion at a cabin in the woods.]
[Choose A: Go. B: Don't go. C: Examine his body.]
[You return to your hometown and discover that an impostor may be hiding in your house. Things have been used, and when you wake up, your palms are damp...]
You play the simulator like every other player, enjoying the thrill of pushing the game's limits and unlocking achievements: [Love Triangle] [Ten-Way Love Affair] [Everyone Admires You] [Everyone Hates You]
Until one day, you've had enough of the game and are about to uninstall it when you see a line of text--
[The impostors have entered your life ^ ^]
Knock, knock.
A sound comes from the door.
--Will you open it?
A blend of □□ Foundation, impostor investigations, American horror, suspense, survival challenges, and management.
Basically, both normal people and impostors will try to seduce the protagonist. The protagonist examines their bodies and various functions to determine whether they're impostors, then upgrades the bureau. (...?)
The blurb may change,
but that's the basic idea.
Theme: Believe in yourself