|Kanji:||石蕗 幸次（つわぶき こうじ）|
|Manga Debut:||Chapter 24|
Kouji Tsuwabuki (石蕗 幸次, Tsuwabuki Kōji) is a lightweight boxer from Tsumugi Gym that faced Riku in the first round of East Japan Rookie King. He used to be a kick boxer, but due to his leg injury, he had to quit and switched to boxing. His girlfriend is Aoi.
While being in Tsuwabuki's apartment, Tokorozawa saw bracket sheet for the upcoming East Japan Rookie King tournament. He asked Tsuwabuki if he was participating and then wanted to how him his skills. Tsuwabuki tried attacking Tokorozawa, but instead got easily punched. As Tokorozawa gave him a lesson of his weak points, he told him to get stronger until the next time he comes to collect the debt. At the gym, Tsuwabuki was training hard, following the advices of Tokorozawa, his growth was noticed by the Tsumugi chairman, commenting to himself that Tsuwabuki covered those weak points of his. Tokorozawa started coming more often and training Tsuwabuki. Eventually he was surprised at how much Tsuwabuki had improved.
As his fight with Riku started, he was feeling his blows as very sharp bladed tools. Even though he was getting punched a lot, he was feeling his punches light, due to his training as kick boxer and taking kicks. He managed to corner Riku at the ropes and exchanged some blows, but got countered and downed by him. In the second round, they both started exchanging blows at close range, but Tsuwabuki managed to do a body blow and down Riku. Third round continued similar, until Riku by listening of Tsuwabuki breathing, was able to read his rhythm and push in to deal a blow and down him. Tsuwabuki was trying to get up, but his head was spinning, feeling like he took a blow in the head by a kick. Remembering his past with Aoi, he found strength to get up. In the fourth round it was a one sided fight with Riku dealing blow after blow on Tsuwabuki. He wasn't going down, knowing that he just have to do one body blow on Riku to defeat him, yet annoyed at his body for no longer listening him, which was just one more of the things he was loosing at. As Tsumugi threw the towel to stop the match, Tsuwabuki was wondering that after he quit boxing, was it over for him and no way to get back up. Riku later visited Tsuwabuki in the hospital, but Tsuwabuki was sleeping.
Power & AbilitiesEdit
Used to be ranked 6th in the lightweight kick boxing, until his leg injury that made him quit. He switched to boxing and went training at Tsumugi Gym, but had a hard time getting used to boxing and forgetting his kick boxing habits. That changed when he met Kyousuke Tokorozawa, who for a short amount of training, made him get rid of all those bad habits and turned him into a much better boxer.
- Loss: As the fight started, Riku was dealing the blows, but even though Tsuwabuki wasn't affected by them and cornered Riku at the ropes. But Riku managed to do a counter and downed Tsuwabuki. In the second round, they both started exchanging blows at close range, but Tsuwabuki managed to do a body blow and down Riku. Third round continued similar to the second as Riku was trying to push in. As Riku was getting close of being downed, he realized that listening to his opponent breathing will make him read his rhythm. With that he was able to push in and deal a blow that downed Tsuwabuki. He managed to get up and the match entered in the fourth round. There it became one sided, Riku dealing blow after blow on Tsuwabuki. As Tsuwabuki wasn't going down, Riku was giving him best to take him down. Eventually Tsumugi threw the towel to stop the fight, leading to Riku's victory.