Zetsuen no Tempest

Yoshino Takigawa was secretly dating Aika Fuwa, the younger sister of his best friend Mahiro. After Aika is murdered under mysterious circumstances, Mahiro disappears for a month and returns wielding magic after making a deal with Hakaze Kusaribe, the most powerful witch of her clan, who has been exiled to a deserted island.

Hakaze promises to help Mahiro find his sister’s killer if he helps stop her brother Samon from reviving the Tree of Exodus despite the danger it may pose to the world. Yoshino joins the conflict while hiding his relationship with Aika from Mahiro, and her death soon becomes entangled with two magical trees and the laws governing reality itself. Between revenge, love, and logic, the friends try to save a world that may be connected to the very loss they want to avenge.