During the East Japan Rookie King Tournament, his boxer, Ryō Mashiba made it to the semi finals and was going against Ichirō Miyata next. In the locker room for the match against Miyata, he told Mashiba to get ready before his fight with Miyata. After Mashiba was almost defeated in the first round, the coach advised him to take his distance and not rush in and became annoyed when it seemed like Mashiba was ignoring him. Mashiba then won the match, progressing to the finals.
The next day, at the Tōhō Boxing Gym, reporters came to ask questions regarding the accident when Mashiba stepped on Miyata's foot. Preparing for the match against Ippo Makunouchi, he got a fighter that was an in-fighter like Ippo to spar against. He was pleased with the spar's results, believing the tournament were theirs.
When the match against Ippo began, he gave Mashiba advice to not let his opponent get close and to use his Flicker Jabs. The match resulted in Mashiba's loss. He was shocked and stopped Mashiba when he was trying to continue the match, getting thrown off by him. However, Mashiba eventually stopped. Before leaving the hall, he requested Kumi Mashiba to have an x-ray for Mashiba's left arm and jaw.
During the Champion Carnival, as the JBC junior lightweight champion, Mashiba's fourth title defence opponent was Tatsuya Kimura. While Mashiba was training for his match, the coach told him that he has nothing to worry about since he is in good condition. He informed Mashiba that the WBC fifth ranker has a match open, and that if Mashiba defeated him, he would have a chance at the world title match, however, he added that everything depends on his performance in the upcoming title defence. He noted that some people disliked working with him yet that "madness" was a dangerous weapon. He believed if Mashiba kept winning, what would change would not be the people around him, but Mashiba.
On the day of Mashiba's title defence match against Kimura, he arrived to the Kōrakuen Hall with Mashiba to be his chief second. At the ring before the match began, he told Mashiba not to let him have the belt and to be careful since Kimura looked to be in high spirits. In the corner after the first round, the coach was happy with what he has seen so far, and told him to let the match develop as planned and to use a combination to go for it. After the eighth round, the coach asked how was Masiba's damage, but Mashiba wasn't able to respond. He tried to get Mashiba to listen to his advice, but Mashiba fell into a state where he wasn't thinking any more. In the ninth round, the coach believed Mashiba has the advantage in actual strength, thinking that there was no way for him to lose in a straight out battle. When the referee stopped the match since Kimura was unconscious while trying to throw a punch, Mashiba was declared the winner.
When the coach went to congratulate Mashiba, he noticed Mashiba was covered in cold sweat from Kimura's last punch. When Mashiba left the ring, the coach told him the winner wasn't suppose to leave the ring first since he needed to do the interview. Mashiba didn't think he won, but the coach told him that he had a knockout victory. Mashiba thought if he stood there as the winner, it would bring him a lot of shame.
While Mashiba was training, the coach saw Manabu Itagaki and Shinoda arrive at his gym in order to spar with Mashiba to help prepare for Itagaki's rematch against Fumito Makino in the East Japan Rookie King Tournament semi-finals. Knowing that Mashiba doesn't know how to hold back, he reassured Shinoda that he would stop Mashiba if he got out of hand. He was Mashiba's second while he sparred with Itagaki three times a week until Itagaki stopped.
For Mashiba's seventh JBC junior lightweight title defence match in the annual Champion Carnival, Mashiba chose Ryūhei Sawamura to be his opponent. At the Tōhō gym, he informed Mashiba that he can't back out of the match now since the press has already announced that he would be fighting Sawamura, asking if Mashiba was okay with it. Mashiba laughed while asking his coach to confirm if it isn't against the law to kill someone in the ring. Later at the Tōhō gym, he was Mashiba's second as he sparred against Itagaki and two other boxers in preparation for his match against Sawamura. He went to the Kōrakuen Hall to attend Mashiba's weigh-in with Sawamura.
The next day, he arrived to the Kōrakuen Hall to be Mashiba's chief second in his seventh JBC junior lightweight title defence match against Sawamura. During the second round when Mashiba and Sawamura were on equal ground, he was surprised that Sawamura is able to keep up with Mashiba's speed, believing that Sawamura has natural born instincts. During the third round as Mashiba and Sawamura were brawling with illegal blows mixed in, he thought that Mashiba would have the advantage since he is used to brawling, however, he was shocked to see the the two are even in brawling as well. When Mashiba got knocked down from an illegal punch-to-knee combination, and the referee declared a down without a warning to Sawamura, he tried to challenge the referee's decision, but the referee did not hear him. After the third round, he advised Mashiba to focus on recovering and to avoid slugging it out with Sawamura. During the fourth round, after Mashiba got up from his second down, he yelled out for Mashiba to clinch onto Sawamura to survive until the round ends. After the fourth round, the referee warned Mashiba that he would stop the match if he is seen stuck at the ropes. He criticised the referee, telling him that he should have ended the match when Sawamura kicked Mashiba while he was down. After Mashiba realised that he was kicked, he mentioned to Mashiba to not get emotional about it and to only focus on recovering in the fifth round. After the fifth round, he told Mashiba to not back off if it becomes a battle of wills, as Sawamura is more damaged. He watched in shock in the sixth round as Mashiba was hitting Sawamura until he was knocked outside the ring while the referee had the match paused. The referee disqualified Mashiba, making him lose, and Sawamura the new JBC junior lightweight champion. He escorted Mashiba out of the ring, and expressed his disbelief in him.
After a failed attempt to get Mashiba to apologise to Sawamura for the fouls, he brought the JBC junior lightweight champion belt to Sawamura's coach, Karil. He left the room feeling down since they took Mashiba's title and world ranking, wondering what Mashiba will do. Afterwards, Mashiba was suspended from boxing for a year.
While Ippo was training for his match against Malcolm Gedo, the coach received a call from Ippo's coach, Kamogawa Genji, asking him to have Mashiba spar against Ippo, which he accepted. When Kamogawa and Ippo entered his gym, he explained how Mashiba's suspension is almost over, and that he will have an OPBF title match as his return match, noting that the champion is a bull rushing boxer just like Ippo. He acted as Mashiba's second for his spar against Ippo. Afterwards, he asked Mashiba why he stopped instead of finishing Ippo off. He was surprised when Mashiba claimed Ippo was aiming for a dual exchange despite being half-conscious, deeming Ippo a boxer that causes a lot of pressure. When Mashiba wondered if Ippo's upcoming match was the reason why Ippo was so worked up during the spar, he mentioned that Gedo's record isn't impressive, but the Kamogawa gym seems to be cautious since they chose Mashiba as a sparring partner.
On the day of Mashiba's OPBF lightweight title match against Aaron Domingo, he went to the Kōrakuen Hall with Mashiba to be his chief second as the match began. After the ninth round, he advised Mashiba to remember what he practised and prepared for. After Mashiba won by knockout in the tenth round and became the new OPBF lightweight champion, the coach gleefully held the champion belt. The coach asked if Mashiba wanted to wear the belt and do a victory interview, however, he declined and walked away from the ring.
At the Tōhō gym, when Mashiba was angry that Kimura lost the Class A Tournament finals, the coach wondered if he was cheering for him. Mashiba explained to the coach how the only time Kimura did anything good was against him, and feels like it puts him in a bad light, wanting Kimura to win sometimes to show that what happen in their match wasn't a fluke. The coach asked him if he wanted to know the results of Aoki's Class A Tournament match since he is in the same weight class, however, Mashiba deemed himself above national level, and knew that Aoki wouldn't be doing his usual mud fighting since he is fighting a no-name rookie.
When Mashiba's first OPBF lightweight title defence against Romeo arrived, he went to the Yokohama Arena. Since Mashiba and Takeshi Sendō shared their changing room, the two argued and injured each other while he and Sendō's coach, Kazuhiro Yanaoka, tried to hold them back. When the match was beginning, he walked with Mashiba to the ring to be his chief second, and had him calm down since he was riled up from fighting with Sendō. The match ended in Mashiba's victory by knockout in the fifth round. He followed Mashiba back to the changing room, and tried to hold Mashiba back again when him and Sendō started fighting again, wondering if it is their way of encouraging each other. He watched Sendō's match against Jose Nargo, where it ended in Sendō's victory by knockout in the eighth round. Once Sendō got back, Mashiba and him argued again, causing the coach to have to hold him back once more until Mamoru Takamura, the WBC middleweight champion, and Richard Bison, the WBA middleweight champion's match began. He watched as Takamura won by knockout in the sixth round.
At the Tōhō gym, the coach was requested by Mashiba to have his next challenger be strong and sturdy, as he wanted to test how much stronger he had gotten after moving up weight classes, and if he would be short on power, in what way he could adjust his fighting style. The opponent was decided to be the JBC lightweight champion, Shinobu Iga. The day before the match at the weigh-in, Iga's trainer, Kurita Baron, revealed that he knew three weaknesses that Mashiba has, and would use them in the match. The coach told Mashiba to not let Baron get under his skin. The next day, he went to the Kōrakuen Hall with Mashiba to be his chief second against Iga. When the match began, he was impressed with Iga's ability to get back up from the uppercut during the first round, and if he kept it up for the coming rounds, Iga's toughness would be far beyond than expected.
During the second round, Iga began using fouls, making Mashiba angry, and he was worried about what Mashiba will do to his opponent once angered. When Mashiba returned to the corner after the second round, the coach claimed that Iga's strategy coincided with a few of Mashiba's opponents and that the fouls were accidents. The referee warned him of his boxer fouling, making the coach argue that Iga was the one fouling. Before Mashiba left the corner, he told Mashiba to box properly like a champion would. He then warned Mashiba, after he claimed that he would make Iga regret fouling, that he shouldn't, as he would forfeit the match and his license. When the crowd began cheering for Mashiba, he asked Mashiba if he thought he was alone now. The match ended in Mashiba's victory by knockout in the third round. After Mashiba answered the interviewer's questions in the ring, the coach announced that they would be relinquishing the OPBF belt and challenge the world for the next match.
With Mashiba having a world title preliminary match against former WBA lightweight champion Juan Garcia, he had a encouragement party held for him. The coach went to the party and heard information about Juan's history and boxing abilities from Ippo. On the day of Mashiba's world title preliminary match, which Itagaki's match against a Filipino ranker is the semi-final of, the coach went to the Kōrakuen Hall. After Itagaki's match, which ended in Itagaki's victory by decision, the coach arrived to the ring with Mashiba as his match against Juan was about to begin. The match began, and, after the first round, the coach was grateful of Ippo's advice, and knew that the old Mashiba who would get in slugfests would have gotten beaten before the round was over. He reminded Mashiba that this isn't the highest point, and encouraged him to remember what he accomplished so far and to believe in himself. After Mashiba defeated Juan in the seventh round by knockout, the coach went into the ring to congratulate him. After Mashiba used the microphone that was for the victory interview to yell at Ippo and almost fell because he lost balance, the coach and the rest of the seconds left the ring to take Mashiba to the doctor.
He is an older man with black short hair and wrinkles. He is always seen with silver coloured round eyeglasses. His attire is usually his gym's shirt with the gym's name on it.