Misaki Tanaka (田中ミサキ, Tanaka Misaki) is the adopted daughter of Jiro Tanaka and his helper in his avenger business.
Misaki wears a blue dress with one strap over her right shoulder like her foster father Jiro. She wears a plain t-shirt underneath and her light brown hair is usually pulled up in pigtails.
Misaki was exposed to the cruelty of the world at a very young age due to her abusive upbringing under her step-father. This has shaped her to mature faster and adopt an extreme dislike for anyone who commits atrocities and crimes. She is remarked to talk more like an adult than a child, but she is not without some childish tendencies, such as when she insisted on keeping the black cat she rescued or retaining her tendency to view the world in black and white. Other people around her, including her home school teacher, describe her as closed-off and unapproachable, especially with other children around her age.
With her biological mother abandoning her and leaving her with her abusive step-father, Misaki has developed an extreme fear of abandonment, going so far as to help Jiro in his business to prove her usefulness so she can stay with him. She also has PTSD, and cigarettes are her trigger, as she received burn marks from her step-father's cigarette buds in the past. From the combination of the abuse she received daily, Misaki has developed a firm belief to punish 'bad people,' and as such has taken a huge interest in becoming a full-fledged avenger like Jiro.
Misaki had grown up with her mother in the first few years of her life and then lived with her step-father when her mother married. However, her step-father was an abusive alcoholic and would lash out at her mother or herself frequently. Unable to bear with the abuse but not willing to save her daughter, her mother left Misaki behind at four years old to be the sole recipient of her step-father's abuse.
On one particular day when her step-father went farther than usual, Jiro suddenly showed up to beat up the man and fulfill a job he had received. When Jiro noticed Misaki hiding in the closet, he beckoned her out and took her straight to Saeki's clinic to care for her injuries. She was given a bath and a warm meal by Jiro, as she was underfed, and from then on, Jiro continued to keep her under his care and at some point fully adopted her. Later on, she began to help Jiro with his avenger jobs by getting his targets to let their guards down, making them easier to capture.
Mayor Harada Scandal Arc
Jiro and Misaki visit the Yamazaki residence and introduce themselves to the family's son, Shota. Misaki puts on an act, pretending to be in awe of the spacious home, and runs inside. She heads directly to the bathroom and finds a black cat alongside hammers, knives, and other tools for torture. After Jiro explains the existence of the avengers, he and Misaki bind Shota and put him in their van. Misaki brings the cat along and convinces Jiro to let her keep it.
That same day, they head over to the apartment of their next target, Jun Murase. Saitoh, pretending to be Murase, greets them at the door. Believing him to be their target, Jiro knocks Saitoh out and Misaki binds him before putting him into the van. After several hours of searching, they are unable to find Tatsuya Yamashiro and Masaki Yoshida, and eventually Jiro drops Misaki and the rescued cat off in order to carry out the more brutal half of the job.
After Mayor Harada's crimes come to light, Misaki attends the Ramens' first baseball game with a full crew. Two months after the scandal, Misaki accompanies Jiro and Martínez in stealing a statue from a robber's house. They arrive at the scene to find two men dead. They hurriedly carry the stolen item from the apartment before others arrive.
Niwaka Samurai Impersonation Arc
Misaki helps Jiro capture Abe for one of his avenger assignments by approaching Abe, getting him to let down his guard, and injecting him with a muscle tranquilizer.
Shou Wang Arc
A month after the story's conclusion, members of the Tonkotsu Nine gather at Bar Babylon to drive to a fireworks festival together. Misaki wears a pink yukata and enjoys the fireworks with Jiro and the others. In the anime, she has more of an active role in the arc, appearing at the internet cafe Enokida and Xianming Lin meet in and attempting to deceive Suzuki in order to infiltrate the Kakyuu Association's headquarters.
Misaki's school is holding class performances, and Misaki has been cast as the heroine in her class' original play, The Bamboo Kingdom and the Mushroom Princess. She is not excited about her role and hesitates to ask Jiro help her make a costume, but Jiro is overjoyed. The next day, however, Misaki sadly announces that the play has been cancelled and she will not need the outfit Jiro has already made for her. She feels greatly upset and guilty for making Jiro waste his time, but she promises to sing for him at the class recital instead.
Jiro and Misaki skip a practice match with the Ramens to work on her essay for school. She initially writes about her admiration for Jiro and her desire to become a full-fledged avenger like him when she gets older, but Jiro, despite being touched by her words has Misaki rewrite it. She is annoyed and unsure of what else to write about until she mentions wanting to join the boys' baseball team. The next day, Misaki waits for Jiro to come pick her up from school, admitting she dislikes school and confronting him on his salaryman state of attire. Jiro initially tries to deny he is dressing and behaving more masculine for her sake, in order to keep rumors from spreading about their family, but Misaki only grows more frustrated with how much Jiro is sacrificing for her sake. In an attempt to make her feel better, Jiro takes her to get sweets before heading home.
The following day, Jiro is contacted for an avenger job. Misaki tries to persuade him to bring her along, but he for the first time adamantly refuses to do so, and she is left at home. Angry and frustrated by her helplessness, Misaki decides to run away from home and heads to Banba's office to seek help, requesting that he teach her how to kill people so she can help Jiro with his work. Lin reprimands her harshly, however, unintentionally reciting her worst fears: that she is powerless and Jiro only finds her to be a hindrance. Misaki storms out of the office in a rage, turning off her cell phone and heading to Enokida's internet cafe. There, Enokida calls Jiro for his location, and she heads for bar where he is meeting with his client from the Mutagawa Group. When she arrives and peers in through a broken window, she sees the clown Méqué hanging dead bodies round the bar's interior. He spots her spying on him and grabs her before she can run or scream.
After driving away from the city center, Méqué brings Misaki into the back of his RV with him. Through her terror, she begins following the training Jiro had given her in case of a kidnapping, and she begins questioning the creepy clown for a motive. Determining the clown to be mentally unstable, she agrees with everything he says, and he asks her to be friends with his other personality. Upon meeting the other personality, she recognizes a piece of herself, the small, frightened, abused child she used to be, and begins to comfort him.
The following morning, Misaki and Méqué begin to talk, and she begins to understand him more. The two end up talking all day, sharing the secrets of their abusive childhoods and how they had coped with the pain and fear. That evening, Misaki asks Méqué to attend the Houjouya end-of-summer festival with her, where they have such a good time that she forgets her plans to escape from him. Afterword, Misaki convinces him to let her go home with the promise that she will call him again. On the walk to the nearest subway station, however, a car pulls up alongside her, and without warning, a man grabs her and drags her inside.
A short while later, she finds herself in a dog cage inside a warehouse, surrounded by several other dog cages containing children her age. She leaves a hair tie on the warehouse floor and eavesdrops on her kidnappers' phone conversation, hoping for information she can use. As the men begin loading the cages into the back of a truck, Misaki captures Hiroshi Ishihara's attention by calling him by name and asking if he is a human trafficker. Alarmed by her lack of fear and curious about her knowledge and history, Ishihara brings Misaki to his home for questioning. When they arrive, he immediately brings Misaki into the bathroom and holds her under the ice-cold water in the filling bathtub. Cold and in pain, Misaki still refuses to tell him about Jiro, and as soon as he is distracted, runs to a nearby closet to hide. As Ishihara roughly pulls her out, she is assaulted by fear and traumatic flashbacks of her step-father, but she refuses to show it, biting the man's arm and taunting him. As he pins her down and begins beating her with intent to kill, Jiro forces his way into the apartment and attacks Ishihara. He continues beating the man well after the yakuza loses consciousness, and Misaki leaps into his arms, relaxing immediately and crying herself to sleep from stress and exhaustion.
Jiro forces Misaki to resume her normal activities, asking Martínez to pick her up from school each day in case of retaliation from the Mutagawa Group. The following week, as Misaki eats a dinner Jiro prepared for her, she realizes too late that he had put a sleeping drug in her juice. When she awakens, she is in a park with Lin waiting for her new foster parents. Feeling lonely and lost, she gives in to her fate, but is surprised when Lin gives her a piece of paper with Jiro's number on it, inviting her to come home when she has grown up and given a normal life a try.
Upon meeting her foster mother, Misaki smells cigarettes and immediately realizes something is wrong. When asked for Jiro's phone number, Misaki gives her Méqué's number instead. The serial killer clown arrives at the warehouse where Misaki is being held by the Mutagawa Group and, at her request, begins killing Sanjou's subordinates to rescue her. She promises to help him if he ever needs it in turn, and she waits inside the corpse-filled warehouse for Jiro to find her. When he comes to get her, she threatens to turn herself in to the police, and he relents and brings her back home. A short while later, Misaki has joined the boys' baseball team at school. As she warms up with the Ramens before a game, wearing a Ramens uniform of her own, she promises to take Lin's position as shortstop someday.
- Misaki's surname Tanaka means "field, rice paddy" (田, ta) and "middle" (中, naka), which literally means "dweller in the rice fields." It is one of the most common Japanese surnames.