Kato Kachiro is a 1st-year at Seishun Academy, and is one of Ryoma's friends and supporters. He is in Class 5 and is usually seen with Mizuno Katsuo and Horio Satoshi. Although he is not very good at tennis, he thoroughly supports the team. He can often be seen cheering for Echizen and the rest of Seigaku at any match. During the monthly Seigaku ranking tournament, Kachiro records Kaido's match for Ryoma, taking a hit in the eye in the process.