A twenety-six year old Japanese woman called Mizuki Ando regularly forgets her name, though only when people ask her about it. She got a bracelet engraved with her name on it. She works at Honda at a job her uncle found for her. She thinks she would be good at sales but is not allowed to earn commission, despite her skill and gaining customers. Her job is to get coffee, answer the phone, and show customers to the lounge. 

She eventually goes to a doctor to be examined as she fears she may have a disease. The doctor dismisses her. She sees a flier for a new counselor, Tesuko Sakaki, who is offering a low rate per session. She begins to go to counseling in the hopes that she may find answers to her forgotten name.

Sakaki explains that her husband works in the Public Works Department and was able to help her start her clinic so rapidly. They begin counseling.  Mizuki tells her about her life, her marriage, and her typical coming-of-age. She also tells her that she is here because she often forgets her name when people ask who she is. 

Mizuki’s life is quite dull with no great problems or successes to give it color. She feels as if she is boring her counselor with her quiet life. However, when the meeting ended, Mizuki felt as if a great burden had been lifted off of her. She agrees to see the counselor the following Wednesday. 

At the next session, Sakaki inquires about any instances in Mizuki’s life which may have had to do with names. Mizuki can only remember one instance from her time at an all-girl’s school. Her parents sent her to an all girl’s school in a faraway town because her mother had gone to that school in her youth. Her parents did not send her older sister away as her older sister was ill. It was at this school that Mizuki had an encounter with a beautiful classmate Yuko Mastunaka. Mizuki was a senior at the time and was therefore student representative of the dormitory. Each student had a name tag which was color coded on their door. The colors correspond to whether or not a girl was in or out of the dorm. If there was no nametag, that meant that the girl had gone away for a while. 

One night, Yoko came to Mizuki’s room and asked if they could talk about something. Yoko was the most beautiful girl in the dorm, though Mizuki suspected that she was actually quite lonely. Mizuki was taken aback when Yoko wanted to talk; they had never had a close personal interaction prior to this. 

Yoko asks Mizuki if she had ever felt jealousy. Mizuki says she doesn't think she has ever felt that. The two discussed this for some time. Yoko explains that jealousy is like a tumor and has nothing to do with personal circumstances. That is, one does not necessarily need to be disadvantaged or without, to be jealous of something else. Mizuki wonders what it would be like to live Yoko’s life; to be so lovely. 

Yoko interrupts Mizuki’s thoughts and tells her that she is going home for a funeral and will be back on monday. She wants Mizuki to hold on to her name tag for safekeeping as she fears a monkey might steal it while she is gone. 

Mizuki thinks it is weird for Yoko to joke around like this but agrees to hold the nametag until she returns. 

On monday, Mizuki reports to her supervisor that Yoko never returned. They find out that she had never gone home and that no one in her family had recently died. A bit later, they find her body in a wooded area. She had committed suicide and left no note or reason behind. 

Mizuki tells her counselor that she never told anyone about her interaction with Yoko as she did not want to cause any more trouble. She never returned the name tag as the more time passed, the more odd it would be for her to return the nametag. She tells her counselor that she has both her nametag and Yoko’s name tag at home stored in a cabinet. 

After her appointment, Mizuki goes home to look for the nametags, but finds that they are missing. 

She continues going to counseling and finds that while she still forgets her name, it troubles her less and has not gotten any worse. After two months pass, Mizuki arrives at her ninth counseling session. Her counselor tells her that they should soon arrive at the true cause for her forgetting her name. At her next appointment, Sakaki tells her they have found the cause for her forgetting her name and that she won’t be forgetting it anymore. She hands Mizuki the two missing name tags in it and tells Mizuki that someone has stolen her name and that is why she cannot remember. She explains she and her husband’s crew in Public Works caught the individual who stole the names. Sakaki takes Mizuki to meet the crew and the thief. Once they arrive to meet the others, the entire group enters another room to introduce Mizuki to the thief. 

Sitting on a chair in the room is a monkey. They explain to Mizuki that this monkey broke into her apartment and stole the nametags. This was about the time that Mizuki began forgetting her name.  Mizuki is confused. Sakaki reassures her that she has many skills and is quite the talented oddball clinician. Her husband reaffirms this. 

The monkey begins to speak and apologizes for stealing the names and bananas from Mizuki’s apartment. The monkey explains that stealing names is a sickness which he cannot control. He had always been infatuated with Yoko’s name but was not able to steal it until he found it in Mizuki’s apartment. The therapist explains that she had a hunch that some creature was stealing names and put her husband on the case. The husband eventually found the monkey. 

He further explains that he was not related to the events of her death, but rather, that a darkness inside of her led to that. The monkey explains that when he steals names, however, he is able to steal goodness and badness from people as well. That is, he becomes attuned to the intricacies of the person’s humanity. Mizuki says she will forgive him if he tells her about herself. He says that he knows something about Mizuki. He explains that it is that her entire family does not love or like her. The monkey further explains that she likely does not love her husband and has become intertwined with her own defensive nature. The words hurt Mizuki but she agrees that they are true. She says they should release the monkey and that she forgives him.

The group eventually agrees to release the monkey so long as he promises never to return and to stop stealing. Mizuki gives the monkey Yoko’s nametag and they say goodbye. Mizuki tells her therapist that now that she has her name, she no longer needs counseling and must face these hard truths on her own. However, she asks if she may return to counseling later if she needs. The therapist say that is fine.

Once she is home, she puts her nametag and the engraved bracelet in an envelope in a box and is satisfied with finally having a name of her own.