Iroha Mayuzumi (黛彩葉, Mayuzumi Iroha) is a character in the Izaya-centric novels and currently a driver for Yuuki Usubara.
Iroha is described as slender, yet very muscular woman, having short hair with one part of her bangs covering one eye.
While she was an assassin, she briefly mentioned not believing that she was built for it due to how compassionate and caring she is. Though she adapted to it overtime despite this. Iroha is also shown as really liking kids, worrying herself a few times over Haruto and how she doesn't want to see him cry if something happens to Izaya.
Iroha was abandoned by her family at a young age only to be taken in by an organization and raised to become a killer. This organization instilled her with various skills, techniques, and readiness, to perform the murders they wished for her to carry out. A majority of Iroha's targets were people of underground organizations who opposed her foster father, in order to survive, Iroha was required to kill. At the age of fifteen, she was sold by her adoptive father to Ryuusei Takioka.
The name 'Iroha Mayuzumi' is not her actual name, but an alias purchased off another person via Kasane Kujiragi. Following Ryuusei's purchase of her, Iroha's life-long training 'to blend in with the general public' was put to the test. Despite her adoptive father, she was able to adapt herself well enough to blend in with society and be thought of as a one of them. This is shown when she realizes that she doesn't want to kill Izaya as she wouldn't like to see Haruto cry. As a trained killer, her concern with upsetting Haruto is nearly solid evidence of her adaptation.
However, she was purchased and hired by Ryuusei for 'body disposal' work with the 'Third Investigation Team'. Along with that, she also works as a beer server at a local stadium.
When first introduced, Iroha is selling beer near the unreserved seats of the Natsugawara's Stadium during the game. She and Haruto accidentally collide while the boy just bought an ice cream, and having a soft spot for children, Iroha buys him another one and finds it odd when she watches him return with a man in a wheelchair and the old man behind him (Sozoro) immediately noticing he's a dangerous man.
Later on he receives an order from Ryuusei to observe Izaya Orihara while he's called with vice-president Hiura. She changes in bartender's clothes to get near him. This surprises Izaya while he is conversing with Hiura and saw it as an opportunity to slice his throat, however retreated knowing it wouldn't work with Sozoro behind him and leaves the scene to accomplish another order.
She is told to look after the hostages, Haruto, Himari and Yuuki Usubara. She behaves in a polite way with them, fearing the next order will be to kill one of the kids, even though the hostages already suspect what Iroha's job really is. Yuuki offers herself to accompany her when Iroha is order to bring a hostage, knowing it would be better for her to go than the kids. In the way there, Yuuki is knocked unconscious by Fudou and Iroha tries to attend her as Usubara, witnessing the scene, goes berserk. After she makes sure Yuuki is safe, she begins to fight with Usubara rather than Izaya so Haruto doesn't feel sad.
When Yuuki recovers, she manages to stop the fight between the two and offers Iroha a part time job as a driver to continue looking for Izaya.
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