Sugawaras Sibling (tsukki x reader) (they/them pronouns)

Everything is normal in Tsukkis life that it until Sugawara introduces his younger sibling. Now tsukki often fights and argues with y/n but how will things change?......

Keep in mind the story uses they/them pronouns so the story can be for any gender since y/n doesnt have a specific gender set! also i will be using things such as h/c (hair color), h/l (hair length), h/t (hair type), e/c (eye color), b/t (body type), s/c (skin color) h/e (height) because i understand you want y/n to be as close as they can to you. Also dont worry my Y/N isnt a sensitive shy girl that cries over harmless jokes.