Finding himself collapsed in the middle of nowhere with barely any clothes on his back, he was rescued by Kuon and given a name. Having lost his memories: his real identity is a mystery. Neither hard-working nor earnest, his quick thinking is this young man's biggest asset. His complete lack of physical strength greatly worries Kuon.
After multiples conversation with "Mito", he learned he's Mikado's brother the "father" of Yamato. In his earlier life he was a smart hacker, and it's because of his hacking of the database of the "iceman project" the mikado was able to create Akuruturuka for example. Haku was also one of the last humankind's suvivor with his brother after the great calamity that turned every human into Tartari. Before the beginning of the story he's voluntary to become a subject experience for a experience to immunize to Tartari's curse and he was put under cryogenization. He's also the uncle of Anju who is the clone of his deceased niece.
During the climax of Itsuwari no Kamen, he searches for Nekone after she flees, because she was afraid her brother would lose his life in front of Vurai. Oshtor has an advantage and Nekone tries to help him, however his intervention deviates Oshtor's attack from Vurai. Haku tries to protect Nekone from Vurai but Oshtor sacrifices his life, saving Haku and Nekone. Oshtor's soul finally found peace, leaving Haku entrusted with his sister and the princess. For the sake of his friends, and to fulfill his promise, Haku casts aside the name he was given and inherit his fallen friend's mask, choosing to live on as Oshtor.
