Pii Natsu ga Ippai(1987)

Natsume’s first day of her second year at high school is very eventful. For some reason, her new class’ resident beauty Chiyako is determined to be her best friend, and she falls in love at first sight with a freshman, who turns out to be Chiyako’s younger brother, Rui. She soon learns many surprising things about Rui. He is a successful model, but he is also extremely moody, sadistic and malicious. On top of that, he hates summer, which is Natsume’s favorite season. Plain but earnest, Natsume is not put off by any of this and decides to win him over and teach him a lesson or two at the same time!