Doppo's son and current prodigy of Shinshinkai karate. He fights Roland Gustof in round 1 defeating him easily before fighting Hanayama Kaoru and fighting a more even round 2 using his sonic fists technique. In round 3 he loses miserably to Retsu Kaiou getting knocked out in 1 punch. Retsu was impressed that Katsumi could take one of his punches. A rematch in the 'Search of Our Strongest Hero' series is interrupted when the convict Dorian comes into the Shinshinkai building and attacks Katsumi. Katsumi also later trains the convict Doyle in Shinshinkai Karate.

In the anime it is revealed that Doppo is actually Katsumi's adoptive father. The final moments of the anime show him washing up at Doppo's home. He has a fight with Pickle which he loses despite his new Mach Punch technique, and as a result he got his right arm torn off and several limbs broken. He is seen in hospital recovering from his wounds shortly after.