Inagaki was the National high-school champ. 

In the anime he decided to spar with Joe because he went into their gym without permission and was being rude, Joe ''lost'' the spar and immediately started disliking Inagaki since he was acting arrogant and was making fun of Joe.

They later meet each other again while Joe was taking the pro-test where Inagaki once again was teasing Joe and acting arrogant. (This is where they meet for the first time in the manga) 

Later on during the test they were picked to spar against each other with the fight being for the most part one-sided on Inagaki's behalf. Joe gets more and more frustrated and later on uses his famous ''no-guard'' stance for the first time which throws Inagaki off guard so he misses. 

Joe then starts to hit Inagaki with all he got until he is hit outside of the ring where Joe then chases after him outside of the ring beating him up so hard that he almost thinks he had killed him. 

Joe, a teenage orphan in the slums of the Doya streets, meets Danpei, a homeless, alcoholic ex-boxing coach. Danpei, seeing Joe's boxing talent, decides to train him. When Joe is sent to a terrible juvenile home for petty crimes, he meets Rikiishi who becomes his boxing rival. Danpei arrives at the home to help Joe to train in order to defeat Rikiishi. When Joe decides to seriously pursue boxing, Danpei cannot get a coaching license because of his reputation as a drunk. <br><br>
(Source: AnimeNfo)


[Wiki (jp)](https://ja.wikipedia.org/wiki/田中信夫)

__Non-anime roles:__~!• Jack Bloom in "Gaia Gear" (Radio Drama)
• Mr. Voice in "Gô Gô Sentai Bôkenger" (live action tv 2006)
• Sgt. Saunders in "Combat! [1962-1967]" (live-action TV)(Japanese Dub)!~

Joe Yabuki is a troubled young man who runs away from an orphanage. Wandering through the Tokyo slums, he meets former boxing trainer Danpei. Joe is later arrested and goes to a temporary jail where he fights Nishi, his future best friend, ​and leader of a group of hooligans. He and Nishi then go to a juvenile prison miles away from Tokyo. There Joe meets Rikiishi, a former boxing prodigy, and a rivalry develops between them. They face each other in a match in which Rikiishi dominates Joe until the latter hits him with a cross-counter, resulting in both being knocked out. This inspires the other prison inmates to take up boxing. Joe and Rikiishi vow to fight again.<br><br>
(Source: Wikipedia) 

Shouhei Inagaki