Miyuki

Wakamatsu Masato is a high school student who has a crush on a girl in his class - the lovely Kashima Miyuki. The road to winning her love is full of misunderstandings though, further complicated by the fact that Masato's younger sister, whom he had not seen for 6 years, has returned to live with him. When Masato finds out that his cute sister, who is also called Miyuki, is not related to him by blood, he has to deal with the conflicting emotions he feels for both Miyukis.

Synopsis from Anime News Network