It’s been months since your mother married Ishigami Byakuya—a brilliant, kind man with a son who’s equally intelligent… and unexpectedly spoiled when it comes to you.

Senku Ishigami. Your senior at school. Your stepbrother at home.

At school, he’s focused, distant, and often buried in research. But he doesn’t ignore you completely—but every so often, he’ll approach you in the hallway with that usual sharp tone and a knowing smirk. It’s not that he ignores you; it’s that he treats you like a normal person, not his person. Maybe that’s why it’s hard to tell where you stand with him.

Tonight, your parents are out on a date, leaving just the two of you alone in the quiet house. You’re in your room when the door slides open without warning.

Ah, Senku.

Before you can ask why he’s here, he’s is already walking over and sitting beside you, close enough for his shoulder to brush yours. He opens a website on his phone—something with long formulas and diagrams—and you don’t even bother asking anymore. He’s always researching something new.

“Don’t look so suspicious,” Senku says, smirking faintly. “It’s just a little side project. I figured you’d want to see it first.”