Mumei

Mumei (無名, Mumei), a mysterious girl who boards the Koutetsujou and appears at Aragane Station.

Appearance
Mumei is a petite girl with short brown hair and reddish-brown eyes. She wears an indigo ribbon tied tightly around her neck, which suppresses the Kabane virus. Removing the ribbon enables her to access her Kabaneri abilities fully.

Her back is home to a large scar where she was bitten by a Kabane in the past. When active, the scar glows a fiery yellow, in the same way that a Kabane's body glows.

Personality
Mumei generally acts much like a child and can sometimes be seen playing with toys. Even when fighting Kabane, Mumei treats any situation as though it is a game. Despite her apparent immaturity, she understands her strength as a means to protect others.

Although she is rather detached and even ill-mannered towards others, she appears to take interest in Ikoma. Mumei appears to have a soft spot for children as well.

Attack on Aragane Station
Mumei first appears in Argame Station as a guest of Kenshou Yomogawa, head of an affluent family. She witnesses Ikoma defending an innocent civilian from the Bushi and his subsequent arrest. While her caretaker is meeting with Yomogawa, she sneaks away to speak to Ikoma in his cell. She is impressed with his earnest distaste towards humans killing other humans out of fear, but leaves Ikoma when a Fusoujou engine hijacked by Kabane crashes into the station.

She is led away by her caretaker, who reasons that her mission to reach Kongoukaku at the behest of her brother is more important than defending the station. He, however, is revealed to have been bitten by a Kabane and subsequently commits suicide, leaving Mumei to reach the Koutetsujou by herself. She encounters a stray Kabane, whom she kills with a single kick.

Boarding the Koutetsujou
Mumei reaches Ayame and a group of survivors before their garrison is overrun. In order to allow them to reach the Koutetsujou, Mumei engages the Kabane horde herself and quickly defeats them. Afterwards, she meets with Ikoma before boarding the engine, but suspects him to have changed since their last meeting. She enters the Koutetsujou, but decides to fall asleep instead of keeping watch over the train, apparently exhausted by her fight.

When Ikoma is thrown off the train, he lowers the drawbridge for the train despite his abandonment. Although he is beset with despair at his own apparent transformation into a Kabane, Mumei leaps off of the train to rescue him. When they board Koutetsujou again, she defends him from Kurusu's group, revealing that Ikoma and herself are Kabaneri -- something in between a human and a Kabane.

Journey to Kongoukaku
After a tense standstill with Kurusu and the other guards, Ayame defends Ikoma and Mumei, who agree to remain in the rear car of the train. During their isolation, Mumei declares that Ikoma be her shield aboard the Koutetsujou and suddenly begins "training" Ikoma to fully utilize his newfound Kabane strength. She however senses a Kabane on-board the train and leaves the car to find it, which angers Kurusu and the passengers. However, the conflict is ended when the train stops for repairs.

Mumei listens to Ikoma's story about losing his sister, which she says is a common story. She confronts a small mob set on killing her and Ikoma, but leaves when Ayame ends the standoff. She plays with the children, but tells the others that she needs blood to sustain herself. Unbeknownst to the others, Shino, a pregnant woman, had been bitten by the Kabane and finally turned. Mumei quickly kills her, despite Kajika's attempts to stop her. Mumei is shaken when she finds out that Shino was pregnant.

Powers and Abilities
Mumei is a Kabaneri, which grants her superhuman abilities. She is fast and nimble enough to leap across rooftops, and strong enough to fight Kabane in hand-to-hand combat. She first displays the full extent of her abilities when she single-handedly kills several Kabane with limited ammunition and melee prowess, during a time in which fully killing Kabane was thought to be near-impossible.

Although she is not the only character with the physical ability of a Kabaneri, she is among the most skilled fighters in Koutetsujou. She is also an accurate shot with a gun, able to finely pinpoint a weak spot near a Kabane's heart from a considerable distance away. She is sometimes able to detect nearby Kabane.

Mumei is most powerful when she releases her restraint, in the form of a blue ribbon around her neck. However, after fighting without her restraint for long periods of time, she becomes extremely tired and her hunger for blood grows.

Trivia

 * The two kanji for her name mean "nameless".