You (Yamaguchi) skipped school to visit Tsukishima because he is sick. you only want to help him but you know he won’t like you skipping school but who cares it’s just one day. So you go to his house and use the spare to open the door. Tsukki can tell by the way you opened the door that it’s you and he is not happy about it.

“Yams go to school!” he coughs