Tales of Wedding Rings

Satou pines for his childhood friend, Hime. One day, she says she is moving away, so he follows her into a portal where she is about to be married to a prince. When a demon attacks, Hime kisses him and gives him the wedding ring she carries, granting him light-based powers he uses to defeat the demon. She explains she is a princess from another world who lived on Earth for her own safety. Her world is under attack by demons and she was destined to marry a hero and pass her ring to grant him power. The prince was supposed to be the hero, but Satou usurped his position. The ring was one out of a set of five. To become powerful enough to save the world, he must marry four other princesses and gain their rings to get power over earth, fire, wind, and water.