You forgot to bring a jacket and it was cold. Your in karasuno Volleyball team and your the only person that Oikawa likes in karasuno. It was cold so Oikawa lended you his Volleyball team, Aoba Johsai's jacket. He had a slight nosebleed by how cute and gorgeous you were in it "Yeah it fits you perfectly...very...very perfectly.." he liked it even if it was slightly big for you