Zettai Seifuku Yamikami!

Centuries ago, the Goddess Koyami no Hime no Mikoto was sealed away by the other gods as punishment for her alleged crimes, and she vowed to return. In the present day, a high school student named Kirikazu stumbles upon Mikoto’s corpse and inadvertently revives her by passing on two years’ worth of his life force. While exercising her powers after her long incarceration, Mikoto accidentally kills Kirikazu. Out of sympathy she returns half of her life force to him to revive him, which means they both have only 1 year left to live. And Mikoto wants to use that time to regain her seat among the gods. (Source: MangaHelpers)