‘Kashimashi: Girl Meets Girl’
Hazumu confessed his love to Yasuna, but she turned him down. To ease his heartbreak, he went to Mt. Kashimayama where he’d met her first. He lost his way in the mountain, and it got dark. He saw a big shooting star, and when he began to wish, he found something was wrong. It wasn’t a shooting star, but it was a falling space ship. He was involved in the crash. He managed to survive by the help of the alien. However, he became a girl due to the accident during the reconstruction of his body.
Descriptions taken from AniDB.net