[Montage of their childhood – losing TV remote batteries, splitting the last pudding, covering for each other’s lies to Mom.]
[Same panel, but now – Miu asleep on Kaito’s shoulder, game still paused.]
[Miu snatches the console, beats the boss in 10 seconds, and hands it back without a word.]
“She’s annoying. Loud. Eats my snacks.” My Little Sister is Pretty Good -Final- -DomiHo...
“…Show-off.”
“Shut up. I’ve almost got the pattern.”
“You said it yourself, big bro.” [She smirks.] “My little sister is pretty good.” [Montage of their childhood – losing TV remote
“Still stuck on that boss?”
It looks like you're referencing a specific title or fan work:
[A living room at sunset. The older brother, Kaito, sits on the couch, staring at a handheld game console. His little sister, Miu, flops down next to him.] I’ve almost got the pattern
[Small post-credits sketch: Miu waking up and yelling, “DID YOU JUST CALL ME ‘PRETTY GOOD’? THAT’S IT? NOT ‘AMAZING’?”]
“But yeah… she’s pretty good.”