Before high school Zaimokuza was bullied for his large size and Chuunibyou hobbies.
In high school he and Hachiman occasionally partnered up in gym class during their first year of high school. It was the result of them being the last 2 without a partner because they are both loners with no friend to partner with.
Plot EditService Club for help with a request. Yukino initially believes he wants his Chuunibyou syndrome cured. He actually wants them to review his latest Light Novel draft. The Service Club reads and then concludes that his latest novel is trash. Dejected but not wanting to give up, Zaimokuza asks if they can read anything else he brings the club. Hachiman accepts this request when he sees Zaimokuza is just happy to have someone read his work. From then on, he became a regular visitor to the Service Club and sometimes helps with requests.
Zaimokuza meets Totsuka who is hanging out with Hachiman. He struggles to believe Totsuka is a boy and wonders why he is so attractive. Zaimokuza, now entranced by Totsuka, starts going to the Service Club's tennis training sessions to watch. He is present and cheering for Hachiman during the tennis match with Hayato and Yumiko.
Zaimokuza goes to the Service Club one day. He mentions he uses RPG game maker sometimes. He also says he is going to a Light Novel publishers for his workplace tour. As the Service Club wraps up for the day Hayama enters with a request. Zaimokuza is silent and tries to intimidate Hayama with his presence until Hayama greets him by name. After being charmed by Hayama, Zaimokuza leaves in a hurry.
During the Kawasaki request Hachiman calls Zaimokuza, who is supposedly an expert, to help them investigate a maid cafe. While there, Zaimokuza enthusiastically tries to get Totsuka to wear a maid outfit he brought. Yui interrupts and decides to wear it instead, disappointing Zaimokuza. Inside the cafe, its revealed Zaimokuza has never actually been inside a maid cafe and has trouble talking to the maids.
The next day he learns Yui's nickname for him is Chuuni. Zaimokuza is jealous of Hayama and he laughs along with Hachiman, when Saki rebuffs Hayama's offer of help.
When investigating the last place Saki could be working, Zaimokuza shows up with a towel on his head and monks robes. Yukino sends him home for not having appropriate attire to enter Angel Ladder.
Hachiman reads one of Zaimokuza's latest unfinished novels and hates it.
Hachiman is at the arcade with Totsuka when Zaimokuza spots them and intrudes. He promises to show them all the best things to do in the arcade. Zaimokuza irritated Hachiman and Totsuka, while sometimes acknowledging his arcade acquaintances he sees. When Totsuka wants to use the photo booths Zaimokuza says those are for girls and couples, but guarantees he can get them in. The attendant shoos Zaimokuza away but lets Hachiman and Totsuka go through. Zaimokuza manages to sneak into the booth startling Hachiman and Totsuka. Eventually he is spotted by employees and captured.
Later on, Zaimokuza has a request about the UG club (United Gamers, new club, recently started, according to Yukino). He was being bullied by a member from the club. They agreed to settle their differences with a game, Zaimokuza wants the Service Club to cancel the game, or fix it so that he will win for sure. During the game (Strip Daifugo/Millionaire) Zaimokuza keeps helping the UG club win in order to see Yukino and Yui strip. Hachiman throws each game so they have to strip instead. Afterwards the UG club apologizes and Zaimokuza pledges to create a wonderful game of his own.
Zaimokuza imposes and gets pitifully invited to Yui's karaoke birthday party. He did not bring a present. During the party he becomes enamored with Komachi, reveals his blood type (AB), and sings a duet with Hachiman.
In volume 4 Zaimokuza is ignored by everyone. Hachiman avoids him at the mall, Shizuka doesn't invite him to the Summer Camp, and Totsuka doesn't want him to come when he and Hachiman hang out again.
During the summer break Hachiman and Totsuka see a movie. Zaimokuza happens to be seeing the same movie and invites himself to their group afterwards. At first Hachiman is annoyed but they all end up talking about RC cars they had as kids.
Zaimokuza brags to Hachiman that his class will be performing the play he wrote for the Culture Festival.
When Sagami hides from everyone, Hachiman calls Zaimokuza to learn about where all the loner hiding spots were.
Zaimokuza is briefly considered to be the "eye-catching" captain for the red team.
He helped out briefly at the first aid tent during the Festival.
During the boys event Hachiman makes Zaimokuza be the decoy and eventual hero for the red team. Zaimokuza distracts the white team until Hachiman can get close to the other teams pole. Hachiman then distracts everyone so Zaimokuza can rush in and topple the white team's pole.
Zaimokuza joins the Service Club when they go Christmas shopping. He also joins them for the Christmas Event afterparty. His gift for secret santa was a flash drive which Hachiman received. It happened to have the text files for one of his latest novel drafts. Zaimokuza received a cushion.
Volume 7 is the Kyoto trip. On the trip Zaimokuza tells Hachiman about his plans to train swordsmanship at Kuramayama (Mount Kurama).
While in Kyoto, Hachiman, Totsuka, and Zaimokuza play a game of UNO. The loser has to get drinks. While Hachiman is gone Zaimokuza and Totsuka play Old Maid.
In Part A, Zaimokuza is brought in with Totsuka as a judge for Komachi's "Bridal Contest".
In Part B, One day Zaimokuza is practicing Judo moves while Hachiman reads his newest light novel draft. They get caught up in the moment and LARP for a bit before Hachiman realizes what he is doing and quits.
Later on while forming a team for the Judo tournament, Hayama is the one who requests Zaimokuza for the team (Hachiman, Hayama, Zaimokuza). During the tournament, using a combination of size, strength, and excessive sweat, Zaimokuza is able to win all of his matches except the final against the judo team.
Zaimokuza follows the group after Karaoke and shows them around the arcade. He and Yukino get into a Medal Game contest. Later they play a game of Trivia, Zaimokuza is on the boys team with Hachiman and Totsuka.
Hachiman recruits Zaimokuza to help him with his Student Council Election scheme. Because Zaimokuza is an expert in all things Twitter, Hachiman makes him create many false accounts in order to "support" Iroha for the election. Hachiman wants him to use the "Follow-for-Follow" method in order to get the accounts noticed.
Zaimokuza is first excited because people notice his skills, but soon voices his opinion that this is not a proper thing to do.
Zaimokuza helps the Service Club moving things for the Christmas Event.
Zaimokuza mentions he chose Sciences and not Liberal Arts for his his third year courses. It surprised Hachiman since Zaimokuza wanted to be light novel author. Zaimokuza points out there are less girls around and states he is much worse with girls than Maths and Sciences.
When Hachiman wants to isolate himself and Hayama during the marathon he tasks Zaimokuza with causing chaos and slowing the following group down.
After the race at a party, Zaimokuza is seen hanging out with Hayama's victory group.
Zaimokuza is having a career path crisis, he talks to the Service Club about what he wants his job to be. He eventually settles on his original goal of being a light novel author. One of his ideas was to be a self-published author, this gave Iroha the idea for a free student newsletter.
Zaimokuza accompanies Totsuka to the Valentine's Day Event. Its revealed they were ordered by Shizuka to carry boxes of chocolate she bought. While at the event he meets Keika.