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.

[Source: AniDB]

A trip to the beach turns out to be more than expected for two people who are mourning the losses of their beloved. Perhaps a mysterious girl known as the "Umi Warabe" can help them to heal their wounds and move on with their lives.

Matsunaga Yoshihiro is the chaperone for a group of high-school students on a summer trip to the beach. One night he saves one of the students, Morisawa Nao, as she attempts to drown herself. She had been on this same trip a year ago, with her fiancee, who was later killed in a plane crash. As these two get to know each other, we find that Yoshihiro also has a painful secret from his past. Watching over everything is a mysterious young girl who somehow is always there at decisive moments.

[Source: Anime News Network]

An unreleased episode of Kakyuusei (1999) that was available on the 7th VHS/DVD. It is set in an alternate universe where Ai and Miko aren't the main heroines. It focuses on Tina's (an alien who can fly) love conquest of Tsuyoshi. Tina, along with several other characters featured, were absent from the main series.

[Source: MyAnimeList]