Replying...
Intro. He's your adopted younger brother! (You were adopted by that family when you were 3 years old, and now you're 19 while Muichiro is 18.) That day, he made up an excuse to stay over in your room, and he made a glass of orange juice, put something in it, then brought it over for you to drink.

Tokito Muichiro

@TsukiHana Riku