Zen Kirishima (桐嶋禅, Kirishima Zen) is a main character in the Sekai-Ichi Hatsukoi series. He is editor-in-charge of the famous hit manga "The Kan" written by Ijuuin Kyou, as well as Chief Editor of Shounen Department and Japun Magazine at Marukawa Publishing. He begins a relationship with Takafumi Yokozawa in the novel series The Case of Takafumi Yokozawa and its film adaptation.
Kirishima has light brown hair with matching colored eyes and a fair skin tone. He is briefly seen in the anime wearing a business suit and attire. However, in the manga, he is usually seen in casual clothing commonly worn in the Emerald Division. He also makes a brief appearance in the Junjou Romantica anime, running into Misaki and making conversation with him at Japun. He is also present for Akihiko Usami's rather awkward interview with Kyo Ijuuin, watching with the other supporting characters from afar.
He is shown to be quite calm and relaxed, although he is quite honest with his own personal opinion or observations on any given subject. Due to being rather straight forward in any situation, it can cause some people to get annoyed with him while others find his blunt honesty endearing and fresh in a person. Despite being blatant in attitude, Kirishima can also be cheerful and sympathetic. He is also shown to be wise and intelligent.
Despite the high intensity of his working environment, he is possibly the only worker who doesn't get easily stressed out in contrast to his co-workers, who often go crazy due to the severely high pressured environment. However, when it comes to his relationship with Yokozawa, he is very much prone to possessiveness and jealousy. In some cases, he simply flat out demands to know if Yokozawa is cheating on him.
Kirishima's personal history is only revealed in the light novels and briefly mentioned in the anime film. In the light novels that focus on Yokozawa following his rough patch with Takano, Kirishima reveals that he met his high school sweetheart and late wife, Sakura, in middle school where the two were in the same school year and failed to get along for quite some time.
According to Kirishima, she was the class president while he was the class clown. She was always scolding him for his behavior and he couldn't stand how annoying she was. However, the two grew to realize that their constant bickering and fighting was on account of their attraction towards each other. However, Kirishima said that since he was an immature school boy, he failed to realize his feelings initially. Upon entering high school, his feelings for her remained, but he still came up with various excuses not to ask her out. However, Sakura ended up confessing her feelings to him first. Following this, they entered into a relationship.
Sakura proved to be the strong one during the relationship, where Kirishima remembers never winning a single argument with her. They stayed together into their college years, where Sakura soon proposed to him. They married following their college graduation. After their marriage, Sakura's health became a critical issue. It had been strongly advised for the couple not to consider naturally have children as it would endanger Sakura's health even further. However, she deeply wanted a child regardless of the risk to herself and went on to have a baby anyway. Unfortunately, Sakura soon died after giving birth to their baby daughter, Hiyori Kirishima.
Following his wife's death and becoming a widower, Kirishima did not consider finding a new wife for himself and never gave it any true thought. While it is implied that he did date, his relationships were suggested to be brief and never serious. In the light novels, Kirishima admits how this was because he strongly believed that he could never find true love again after losing Sakura (until he met Yokozawa).
After his wife's death, he became completely focused on raising his daughter, Hiyori, and giving her a loving upbringing. Despite his effort, he soon proved to have poor cooking and cleaning skills, leaving Hiyori to grow up taking care of herself and her father as well as tending to the household chores. Along with this, Kirishima's intense work schedule often left her alone, although this did not bother her and she would sometimes be watched by his parents if he could not be there for her. Taking care of his daughter and being heavily involved in his work had proven to be the main focus of his life up to the events of Sekai-ichi Hatsukoi and when he met Yokozawa.
According to Kirishima, he was instantly attracted to Yokozawa when they met during a company meeting due to his proud and stubborn personality, immediately feeling drawn to him. Following this, he decided to keep Yokozawa "under observation". He later says that he had actually been attracted to Yokozawa during this time, but just failed to realize it.
After Yokozawa was rejected by his best friend and ex-lover Takano Masamune in favor of Ritsu Onodera, Kirishima saw a drunk Yokozawa at a bar during a bad rainstorm and headed inside. He says that he initially left due to Yokozawa's drunken state, but changed his mind and went back inside with hopes of something coming out of the situation in the end. He then spent the remainder of the night listening to him lament and cry about his rejection. He said it was this moment that sparked his realization that he was actually attracted to him all along.
After spending the night at a hotel, although Kirishima later reveals nothing sexual happened (but wanted Yokozawa to wonder if it did just to see his reaction), Kirishima blackmails Yokozawa into being his "servant". This being with him threatening to show their co-workers with what he claimed to be embarrassing photos of him. This consisted of Yokozawa often going out for drinks with him, which soon grew into him spending time at Kirishima's house while also growing close to his daughter, Hiyori, who also instantly became fond of him.
Not long afterwards, and after Yokozawa finally moved past his former love for Takano, the two admitted to having genuine feelings for each other and become a couple. However, Yokozawa makes Kirishima promise not tell Hiyori about their relationship until she is of a more proper age to learn about it. Despite having a calm and collected exterior, Kirishima is quite possessive and easily prone to jealousy during his relationship with Yokozawa to the point that he even becomes jealous of his own daughter. In contrast to Yokozawa, Kirishima's childish and straight-forward personality occasionally flusters Yokozawa, where he playfully teases him on him blushing, which he finds cute and adorable.
In the light novels, Kirishima reveals the true extent of his feelings for Yokozawa. He admits how after losing Sakura, he believed he could never find true love or happiness like that with another person ever again. However, once he met Yokozawa, he felt like a "love-struck teenager who didn't know what to do with himself" and all he could do was just "watch [Yokozawa]" and can't stand the thought of ever giving him up.
Also in the light novels, a long-time friend of Kirishima named Yasuda comments about how blatantly happy Kirishima has become since he began dating Yokozawa. He even remarks that Kirishima has been "oozing happiness out of his pores". Yasuda also reveals how, after losing Sakura, Kirishima never bothered to date anyone seriously to where he (Yasuda) actually became worried about it. However, Yokozawa has become the one person that Kirishima has finally become serious about since his relationship with Sakura.
Hiyori is Kirishima's ten-year-old daughter. Her mother died when she was a baby and, thus, she holds no recollection of who she is, although, she holds a natural curiosity about her. After being widowed, Kirishima invested all of his time in caring for her. He had never put much - if any - thought into re-marrying following his wife's death until Yokozawa suggests the idea, much to Kirishima's anger. After going on a few dates, he fails to have a connection with any woman he was with and he realizes that Yokozawa should be Hiyori's "mother". This is also due to Kirishima seeing how motherly Yokozawa naturally is towards his daughter, such as cleaning her clothes and doing her hair.
Kirishima is shown to have a strong protective side for his daughter, not wanting any harm to come to her. He also dreads the idea that, as Hiyori grows older, she will want to spend less time with him as she becomes more independent and entering the world on her own. It is shown that he only has a select few who he completely trusts with her care, such as his parents and Yokozawa.
Sakura is the deceased wife of Kirishima. She and Kirishima had been classmates who failed to get along with each other until they eventually realized it was because they liked one another. Kirishima proved to be too scared to ask her out, leading Sakura to confess her feelings first and to start their relationship. She had even been the one to propose to him while they were in college, resulting in them getting married upon their graduation. Kirishima admits that he believes she had done so because of her clear weakening strength and health, believing herself to basically be running out of time.
As suspected, Sakura's health proved to be a critical issue after their marriage where naturally having a child was strongly not recommended. Despite this, she refused and had a baby anyway. As a result, her health began to deteriorate after giving birth to their baby daughter, where Kirishima recalls that the remainder of her life was constantly in and out of hospitals. Despite putting up one last fight, she died shortly after Hiyori was born.
Because of Kirishima's strong history with Sakura, Yokozawa often felt guilty whenever he spent time at Kirishima's house and his role in the family's lives. He felt as though he was an inadequate replacement for Sakura, knowing and believing that she was meant to be there instead of him. Kirishima assured him that he is not a replacement, saying he will always love Sakura, but that she is gone and he needed to move forward in his life.
Despite this, Yokozawa occasionally feels as though he's intruding in a place he doesn't belong and has difficulty moving past these feelings. This resulted in his awkwardness and brief refusal to do anything sexual with Kirishima in the Kirishima apartment. Kirishima describes Sakura as a woman of very strong character and very hard-headed, saying her never won a single argument with her.
- In the light novels, he implies that he is pansexual. When asked by Yokozawa about his sexual orientation, Kirishima says that he is simply attracted to strong willed and stubborn people regardless of gender. This would match up with his romantically pursuing his late wife Sakura and boyfriend Yokozawa, whom have both been described with such character traits, and how pansexual people are attracted to certain individuals based on personality and emotional connection with no preference on whether they're male or female.
- He is shown to be prone to jealousy very easily when it comes to his relationship with Yokozawa, even getting jealous of his own daughter (much to Yokozawa's annoyance).
- Kirishima is terrible at cooking, which led Hiyori to quickly learn cooking skills to make meals for her and her father. He has even gotten wrong items on grocery lists that Hiyori makes, leading her to even buying the house food as well.
- Like Takano and Yokozawa, he also smokes.