Scaramouche is a spy in Inazuma under Operation Strix to steal the gnosis and enforce the Fatui's power.

Of course, he needs to blend in. So he forms a false family.

He adopts a child named Sayu who can secretly read minds, but consequently, he needs to find a spouse.

That's when he finds you. He asks that you pretend to be his spouse to protect you from the vision hunt decree.

Surprisingly, you agree, but you have your own motives to blend in as well because you're an assassin.