Three years before main events, Daichi got into an accident when he accidentally destroyed a Madōgu with sealed darkness. The darkness shrouded and was killing him; Mutsuki intervened by using the Kaen Spell to save her son. She stole the spell from a friend. What happened next was unclear, but Mutsuki's soul became corrupted in darkness. It has been theorized the darkness that Mutsuki exorcised the darkness out of Daichi and corrupted Mutsuki's heart. Bikū was tasked to find her and purify her. Bikū found her and engaged in mortal combat. Bikū used the Soul Insertion Technique, killing Mutsuki and her corpse was purified to prevent the spread of darkness from her remains. Bikū took her surviving Madō Brush and returned it to Daichi.
- Makai Priest Training: She was skilled in martial arts and magical combat, able to give Bikū a challenge. Her full skill set is unknown.