Zetsuen no Tempest

The point of view begins with Hakaze, a witch who ended up on a deserted island. Changing point of views, we now look at Yoshino and Mahiro. Yoshino and Mahiro were best friends, but one day Mahiro suddenly disappeared. Yoshino assumed that he found a clue to whoever murdered his family. Despite the close bond they had, Yoshino has no idea where Mahiro is. However, one day when Yoshino was putting flowers on Mahiros' family's grave, a woman questions Yoshino about Mahiro at gun point. According to the woman, Mahiro got involved with some serious issues that will inevitably put the human race in a catastrophic situation, and the Japanese government is desperately looking for Mahiro. Apparently some sort of "magic" is involved. What happened to Mahiro? And who is this Hakaze girl? What does Hakaze have to do with this?