Kakyuusei

Kakyuusei (下級生, Kakyūse) is a Japanese anime series about high school romance where the story is individualized into separate sequels and spinoffs. The first series entitled Elf-ban Kakyūsei appeared as a dating simulation game created by Masato Hiruta (Elf), followed by an OVA series based on the game by Pink Pineapple, and later an anime adaptation. The second series titled Kakyuusei 2 (下級生2 〜瞳の中の少女たち〜) is a sequel to the first, developing the game, and anime adaptation by Soft Garage, and 2 OVAs produced by Pink Pineapple.

Elf-ban Kakyuusei
High school students Mizuho Yuuki and Miko Kamiyama are best friends, while Miko has a crush on fellow classmate, Tohru Nagase. Determined not to get in the way of their budding relationship, Mizuho strays apart from the fact Tohru is currently boarding with her family. As the romance grows from underclassmate Ai Minamizato. Tohru must decide which girl he likes the most.

Kakyuusei (TV)
When Tsuyoshi rushed to school as usual, he found a girl who tried to help a kitten which couldn't get down from a tree. It was Minamizato Ai who had loved Tsuyoshi secretly for a long time.

Kakyuusei 2
Many people have fond memories of meeting a certain teenage boy in their younger years. However, their ages vary widely, and each remembers him as a teen. This story follows the intricate intertwining of their various stories and how this young man, who apparently lives outside of time, has affected each of them.