Two Years Prior to the StorylineEdit
Marui began Rikkai Dai along with the rest of the Rikkai 3rd Years as 1st years. He played in the Newcomer's Tournament. Marui won against Akutagawa Jirō.
One Year Prior to the StorylineEdit
They treat Kirihara to ramen after seeing him playing at an arcade and explain how Rikkaidai won the Nationals the previous year and that the best players in the club, were in fact the 2nd years who were the 3 monsters at this time and that the seniors that Kirihara thought were the driving force behind Rikkaidai were nothing compared to their year.
It is shown that during this time, Marui is challenged to a match by Akutagawa Jirou after the latter visits him in his school ground. However, their matches ends after Jirou falls asleep in the middle of the game, shocking both Marui and the rest of the Rikkaidai team.
Marui and Rikkai effortlessly won the Kanagawa prefecture tournament and broke the tournament record for fastest tournament win despite the significant absence of captain Yukimura Seiichi.
Marui and Rikkaidai cruise through to the finals of the Kanto Regional Tournament with ease and visit captain Yukimura while he is in hospital a day before the final, assuring him that they can win the tournament so he can come back to the team with a trophy before the Nationals. Marui pairs with best friend Jackal Kuwahara for Doubles 2 against Momoshiro Takeshi and Kaidō Kaoru pair.
He and Jackal shut down Momoshiro and Kaidō despite the 2nd years' best efforts. He stuns them early on with his Tightrope Walking and volleying skills. He and Jackal win 6-1 after a long match.
Rikkaidai go to the Nationals as underdogs after a shock defeat to Seigaku in their Regional final; however due to the return of their captain Yukimura Seiichi, they expect nothing short of a 3rd Consecutive championship.
The tournament begins as a swift walk in the park for Rikkai Dai as they cruise through past all of their opponents until the Semifinals. At the Semifinals, it appears as though Rikkai Dai are having difficulty against their opponents Nagoya Seitoku from the Aichi region,a team where all the regulars are Western Foreigners.
At first, it appears Yagyū Hiroshi is utterly defeated in Singles 3 by one of them. Then in Doubles 2, it appears that Marui and Jackal are also outclassed. With everything seemingly relying on the shoulders 2nd Year Kirihara Akaya who plays agaisnt Nagoya Seitoku's ace Liliadent Krauser. Krauser effortlessly jumps to an early lead and dominated Kirihara with his power and Hopping Ball shot. Until suddenly Kirihara activates Devil Mode and makes a 7-5 comeback annihalating Krauser. Marui, Jackal, Yagyū and the rest of the team laugh and smile at Kirihara after his match and reveal that they werent playing seriously at all and only lost on purpose just as to make Kirihara activate Devil Mode to help ensure victory for the finals. Rikkai then win the next matches in Doubles 1 and Singles 1 and advance to the finals.
Marui and the Rikkai Dai team decline Seigaku's invitation to join them at a Yakiniku bar. Unbeknownst to both teams, they had just turned down an event that would become a large eating contest.
Prior to U-17 CampEdit
Sometime prior to the U-17 camp, Marui, Jackal, and Kirihara shop for materials for Rikkai's Ocean Festival. While shopping for materials, Marui and Jackal bump into Kawamura Takashi of Seigaku who was visiting a relative in a hospital in Kanagawa. Kirihara arrives shortly and suddenly a dog jumps into a Kirihara and runs away with the stuffed toy that was in Kirihara's hand.
The four of them give chase to the dog until Kirihara is able to tackle the dog and retrieve it in the end.
During the Festival, Marui plays Cinderella's (played by Kirihara) evil step-sister alongside Yagyū, the other evil step sister. This can be found in the PairPuri anime.
Later on, the Rikkai Regulars continue training after the Nationals. During this time shown in the Pair Puri, Yukimura encouraged his teammates to have fun while playing tennis, however they comically went about it the wrong way and decided to scrap the idea. Later, Yanagi introduced the Rikkai Dai tennis club members to Inui Juice, after staying by Inui Sadaharu's house the night before. Yukimura arrives to a defeated club as Marui and all the other members that tasted the juice were unable to stand, besides Sanada who was in tears after tasting it but stayed standing nonetheless.
Marui Bunta and all of the Rikkai Dai regulars More characters Yukimura Seiichi, Sanada Genichirō, Yanagi Renji, Hiroshi Yagyū, Masaharu Nio, Jackal Kuwahara and Kirihara Akaya receive invitations to the All-Japan Juniors Training Camp. Marui Bunta and all of the 50 middle schoolers are told to catch a ball from the helicopter and those unable to obtain a ball must go home. Marui and all of the 50 middle schoolers who were there at the time were able to catch a ball from the helicopter causing only High Schoolers to be sent home. He plays against an unknown high schooler that is awed by Marui Bunta's Tight Rope Walking technique.
The Mental Coach arrives and declares that all middle schoolers must pair up. He then coldly says that the person they have paired with, is their opponent in a tie-break game and the loser must go home. Marui as expected paired with best friend Jackal. Marui is victorious after a tight game winning just 10-8. He and the rest of the Rikkaidai regulars watch the match between Yanagi and Kirihara.
Jackal is believed to be sent home while Marui stays and defeats his next high school opponents in the Player Shuffles that all the winning Middle Schoolers take part in easily and reaches the 6th Court along with fellow Rikkai Dai teammates Yagyū and Yukimura. While Jackal goes to the mountains with all the other Middle school losers and comes back to the camp as a member of the 2nd Court.
U-17 Camp RevolutionEdit
Marui is present with all the other members of the camp at the main court to see the return of the Top 10 and are also present when it is revealed that Middle Schoolers have replaced No.s 11-19. Marui later bumps into Kite Eishiro when looking to have quick practice session.
Genius 10 ChallengeEdit
After Atobe Keigo and Niō defeat Ochi Tsukimitsu and Mōri Juzaburo, Gin is defeated at the hands of Duke Watanabe, Kite and Marui prepare to take on Atsukyo Tono and Kimijima Ikuto for the 3rd Match. The audience comment that Kite and Marui make a good doubles pair. Soon however, Kite seems to betray Marui, making it a 3-on-1 game. Kite does this simply because Kimijima asked him to betray Marui.
However it was also later revealed that Kimijima was sick and tired of having Atsukyo as his doubles partner and asked Kite to pretend to betray Marui so as to find the perfect opportunity to injure Atsukyo. Just as Kite was preparing to give Atsukyo such a blow however, Marui, pushed to his limits, is able to achieve a new skill, "Perfect Fortress", blocking all the shots at the net, preventing Kite from reaching the ball. Kite is moved by Marui's willpower and when Kimijima lobs a ball high to pass Marui, instead of attacking Marui again he uses his Habu and hits Kimijima instead.
From this point on, the two begin to work together, establishing a bond of trust between them, with Marui staying at the net and Kite gets any ball that goes over his head. Marui blocks several of Atsukyo's "Executions", but falls victim when Atsukyo throws his racket at his right eye. Still willing to play the match, he goes back in with a bandage over it. However, with his right eye covered, his Perfect Fortress is now vulnerable on that side. As Atsukyo prepares to show off more of his "Executions", Kite runs in front of Marui and takes the hit in the face. Kite then tells Marui to stay back and let him get the front.
Marui realizes that Kite feels guilty for his actions earlier in the match and is seeing this as a way to redeem himself. When Kite takes the last "Execution" Technique, Seppuku, Kimijima interferes with Atsukyo's shot and hits it to Marui, who then smashes the ball into Atsukyo's left kneecap. It is then revealed that like Kite, Marui also made a deal with Kimijima; if Marui smashes the ball into Atsukyo's left knee, then Kimijima will arrange for Yukimura to receive a special surgery in America that will fully heal him of his disease.
The match is then finished by Kimijima, and he discreetly tosses Atsukyo's U-17 Badge at Marui's feet. Marui proceeds to take Kite to receive treatment as Kimijima tells him that someone should be contacting Yukimura about the surgery within a few days.