Reiji Azuma (Zwei) and Elen (Ein) stayed in Japan 2 years after the incident in C.A as brother and sister. Mio is in the same class as Elen and she is secretly in love with Reiji (Zwei)
Mio is actually the secret daughter of the Yakuza involved with Inferno and her supposed uncle is actually her blood brother from the same father. Because of her being on earth, the head of the Yakuza kept her as a secret to prevent any situations arising that ties the Yakuza to her. But she is later discovered by the scythe master, who passes the information down to Ein. Ein uses this to her advantage and along with Reiji, befriends her as a backup plan should the need arise.
Mio is the first to witness Cal Devens confront Reiji, when she punches him down. She is then later kidnapped by Cal and held hostage in an abandoned school dormitory. Regardless of the position Cal placed her in, Mio felt slight sympathy for Cal. After being told by both Cal, Ein and eventually Reiji himself that their past lives were murderous, she continues to feel love for Elen and Reiji and is also the only character shown wishing the two a distant farewell after the night clash with the Zwahlen sisters and the scythe master.