Three years later, he won the National High School Rugby Tournament in Hanazono.
Sonoda was named as captain four years later and would be selected as a university representative for Japan.
Since joining the team, Sonoda suffered injuries such as left wrist fractures and left knee ligament injuries, and Masami Horikoshi was already the starting scrum-half, so Sonoda could not have the opportunity to participate in the match.
Sonoda received his first cap for Japan during the test match against Fiji in Tokyo, on 20 May 2000.
He was also part of the Japanese squad coached by Shogo Mukai for the 2003 Rugby World Cup, playing four matches at the tournament, with the pool stage match against United States, in Gosford, on 27 October 2003 being his last international test cap.