One day, he beat up several boxers from Naniwa boxing gym, and met his coach, Yamaoka. He soon became interested in boxing, going on to win the Western Japan Rookie Championship. As a result, he was slated to fight Ippo who defeated Ryo Mashiba to become the Eastern Rookie King Champion, during the All Rookie King Japan Tournament. However, during the fight with Mashiba, Ippo injured his right hand and as a result decided to skip the fight with Sendo. After finding out Sendo literally goes out of his way to make Ippo change his mind and after seeing his determination to want to fight him so badly akin to his desire to want to fight Miyata, Ippo decides to go on with the match despite his handicap. In the end Sendo loses the fight by TKO, however despite this Ippo was left feeling that the battle hadn't been fully resolved, since he was clearly losing the fight and was barely able to walk when the 4th round was about to start but Sendo remained in his corner unconscious due to a punch that Ippo connected to his temple.