Mugenji is a homicidal murderer, driven insane with his abnormal obsession with beauty and butterflies. As a child, he was ostracized by his village for his unruly appearance, often driven to live alone in fields of flowers. A blind girl, named Ocho (whose name means butterfly) willingly befriends him. One day, Ocho excitedly tells him that she will visit a doctor to gain her sight. For dubious reasons -implied to be his fear of her seeing what he looks like- he strangles her to death. Believing that he will be reborn into a butterfly, Mugenji traverses across the land, killing anyone who is in his path.
In his ending, he defeats the Three Blades of Dominion and returns to a field full with flowers and butterflies. He collapses, mortally spent from his wounds. As a butterfly whisks above him, he crushes it.
Mugenji developed a strange philosophy because of inferiority complex from his childhood. According to it, all dark, evil deeds and emotions are welcome, and all light and good things are deemed vile and should be punished. As a self-proclaimed servant of darkness, he needs to constantly slaughter good people as sacrifices to a dark lord - and ultimately purify the land. He acts highly protective towards his "sanctuary" as he believes that others "defile" this sacred area and scare away the butterflies.
- Pollen Cloud - Mugenji can a summon small cloud of pollen and butterflies, which will stun nearby opponents, allowing Mugenji to land a hit.
- Poison Dart - Mugenji can throw his poisoned hairpin which will slowly drain away his opponent's life.
Mugenji's main strength lies in close combat. His normal attacks allow him to keep his opponents near and link together long combos. If he empties opponent's first lifebar with Issen, and then manages to sustain 15 seconds without taking damage (and without completely emptying opponent's next lifebar), a butterfly will come from sky and sit on opponnent. Gameplay effects of this are unknown yet.
His sword is forged in Damascus steel and is believed to not come from Japan. It resembles a large nata with a spike.
- Days of Memories (third title) - in-text cameo