|Entry Level Programmer|
|Nakamura Hiro (Love interest)|
Sugimoto Ai (also known as Radical) is a worker at the same place as Hiro and she admires Mao's cellphone novel.
Sugimoto is described to beautiful and cute even from boys. She currently has light blond hair in a pixie haircut. She used to have longer hair up to her shoulders, but she got a hair cut.  Throughout the story, though, her hair continues to grow a bit longer.
She is usually quiet at work, being one of the few girls at the workplace. She tries hard to talk to Hiro, him being the person she likes. She becomes enthusiastic when she talks about Date Masamune. She loves to talk to her online friend RUIRUI on a daily basis.
Radical has only gone to all girls schools since middle school. She has never really talked to boys before, and didn't think much about dating until she met Nakamura Hiro. She was afraid of him at first, but then realized that he was actually very kind.
- "I'm sorry for having to text you about something like this. I felt like if I didn't tell you this today, I wouldn't ever be able to. I've liked you for a very long time. That's it. I'm so sorry."
- -Sugimoto's text to Hiro 
- Nakamura Hiro is a love interest and colleague of Sugimoto's. Radical started to like Hiro ever since her manager started asking whether she had a boyfriend or not before, Hiro had saved her by asking something to the manager and Sugimoto ran off. This turned out to be the first time Radical had liked someone since elementary school even though she was in her twenties. Whenever Hiro eats dinner with Sugimoto (sometimes with Fujita but other times they are alone), Sugimoto often gets very nervous. Sugimoto often offers to spend more time with Hiro, but Hiro often rejects because he is busy. Sugimoto often blushes very deeply and stutters when she talks to Hiro. She sometimes asks questions to Hiro about Mao because she is jealous about how close they are. She decided to go confess to Hiro during the Sendai trip because Mao had said that Hiro had rejected her (in reality, Mao just told Hiro to forget about Mao's confession). Since Sugimoto had never had feelings for anyone boys before, she is too embarassed to confess to Hiro, so she sends him a text confessing her feelings. Later at work, when Nakamura Hiro tries to confront Sugimoto about the text, she gets nervous and runs away from Hiro because Sugimoto cannot stand Hiro's reply. Hiro finally is able to confront Sugimoto out in the street while it is raining, Sugimoto repeats her confession, and Hiro replies that she is a truly wonderful person, but he has someone else he is commited to. Sugimoto is left out in the rain, and Hiro leaves with an umbrella. She cries a lot about her rejection (her eyes get swollen the next day at work) and tries her best to forget Hiro but finds it extremely difficult. At the end of the story, she is able to come to terms with her feelings and wishes Hiro the best when he transfers to a different department within the company.
RuiRui is Sugimoto's online friend whom she talks to about her love life and whom she gets along with. One day she agrees to meet RuiRui thinking her friend is a girl and learns he is actually a famous model. While she is surprised, she realizes it is him and he confesses to her. He tells her that she was the first person who accepted him for his hobbies, which others thought of as weird. While she is hesitant to enter a relationship at first, upon getting to know him further, she realizes she had already fallen in love and agrees to date him. Because they share the same interests and hobbies, she and RuiRui are able connect and feel much more comfortable with each other.
- "I'm torn between the me who doesn't want to pretend to be you. And the me who wants Nakamura-san to take interest in me because of it. Even if just a little."
- -Sugimoto's thoughts when she pretends to be Mao 
- Sugimoto meets Mao because she is a fan of Mao's cellphone, House of the Sun. Sugimoto(aka Radical) is very welcoming to Mao and she invited Mao to her house twice. When Mao finds a box with pictures of Radical's crush, Hiro, Mao feels guilty because Sugimoto really likes Hiro. Mao eventually tells Sugimoto that Mao likes Hiro also, and lives with him. Radical is very saddened by this and finds it difficult to believe. She cries when she realizes it was true. Sugimoto knows the reason why Hiro only pays attention to her is because Hiro thinks that Sugimoto is the writer of House of the Sun when it is actually Mao. Sugimoto lies and says that she wrote the novel, and she feels guilty about pretending to be Mao. When Mao told her that Hiro had rejected her (in reality, Mao just told Hiro to forget about it), Sugimoto thinks that there is no point in waiting and this encourages her to confess to Hiro. They soon become distant because of their feelings towards Nakaruma Hiro. Sugimoto often worries about Hiro's feelings about Mao, and she knows that she will eventually have to clear up to Hiro that she is not Kuukai, the writer of House of the Sun.
- Fujita - There isn't much interaction between them. However, Fujita usually aks her out to get a drink along with Hiro. One time when they were drinking at a celebration and she becomes drunk, she invited him to drink with her, calling him "glasses".
- RUIRUI - RUIRUI is Sugimoto's internet friend who Sugimoto texts regularly. Sugimoto says that she talks to internet people because they can understand her better. RUIRUI gives Sugimoto suggestions on her love life, first when Sugimoto told her how Nakamura Hiro seemed scary when Sugimoto first met Hiro (RUIRUI tells her to talk to him and don't judge so quickly), and all the way when she says how she had trouble confessing her feelings to Nakamura Hiro (RUIRUI tells her that she's acting like a middle schooler, but says that we all have those moments). RUIRUI and Sugimoto are both big fans of Date Masamune which they call "Maa-kun". On Christmas, they skyped each other and chatted. Sugimoto considers RUIRUI to be very kind person.
- Nakamura Daiki - After Sugimoto got rejected from Nakamura Hiro, Sugimoto often cried and complained to Daiki (making him annoyed) about Hiro at Warring States Themed Bar.
Sugimoto [text to Hiro]: I'm sorry for having to text you about something like this. I felt like if I didn't tell you this today, I wouldn't ever be able to. I've liked you for a very long time. That's it. I'm so sorry. 
Sugimoto [thoughts about Mao]: I'm torn between the me who doesn't want to pretend to be you. And the me who wants Nakamura-san to take interest in me because of it. Even if just a little.
Sugimoto [thoughts about Hiro]: What's this? I can talk with him normally. After that I realized I was over-thinking things and so every day, day after day, I was able to talk with him.
Sugimoto [thoughts]: I want this person to be happy. I've only been thinking - I wonder if Kuukai-san is a piece of Nakamura-san's happiness? - about myself this whole time. I only ever thought about how I wanted to push my feelings onto other people. Whether it bothered them or not. It didn't even cross my mind when I took Nakamura-san here how it would make Kuukai-san feel.
Sugimoto [thoughts]: It's no use. I just can't help myself. I should tell him my feelings during the business trip. Once and for all. But what will happen if he turns me down? How painful will it be? I can't begin to imagine.
- Sugimoto is a fan of Date Masamune and collects lots of historical books and action figures.
- Sugimoto calls Date Masamune 'Maa'
- Sugimoto has very low tolerance to alchol and often gets drunk at the Warring States Themed Bar
|Main Characters||Motomiya Mao • Nakamura Hiro • Nakamura Daiki|
|Supporting Characters||Nakamura Hina • Chihiro • Oda • Sugimoto (Radical)|
|Parents||Hironaka Yuzuno • Motomiya Kaitou • Step-Mother • Mrs. Nakamura • Mr. Nakamura|
|Other Characters||Motomiya Yui • Fujita • Matsumoto Aoi • Otoha • Kokoa • RUIRUI • Date Masamune|
|Animals||Croquette • Wakaba|