Kimi Sae Mo Ai No Kusari summary:

Shouta Koishikawa and Miono Hasuoka are childhood friends and neighbors that are always together. At some point Shouta's heart starts to recognize Miona and around that time Miona was charmed by her science teacher, Professor Kaorumaru, who is not entirely what he seems to be; he predicts the future in which Miono's fated love will "awaken another Miono". Later that day, as Shouta was going to confess with Miono a demon, Ginyasha, appears and takes over his body awakening something inside Miono. So begins Shouta's struggle to control both the demon and future. Everything now spins on the Wheels of Fate that was set in motion hundreds of years ago and is about to come in full circle. -- Shoujo Magic