Ousama no Propose

Saika Kuozaki is a powerful witch who is the only one capable of stopping entities that threaten the world every 300 hours. After she is critically injured, she transfers her powers and body to Mushiki Kuga, an ordinary high school student who finds her. Mushiki now possesses her abilities but struggles to control them. To help save the world, he must attend a mage academy while maintaining Saika's identity and concealing his true self.