[7] At the end of 2012, Matsushima was also invited to attend a training camp for the South African Under-20 team in preparation for the 2013 IRB Junior World Championship.

[9][10] He also played in their quarter-final match against eventual champions Golden Lions, but could not prevent his side suffering a 25–42 loss to be eliminated from the competition.

He made important contributions to Clermont's 2020-21 European Rugby Champions Cup campaign, scoring a hat-trick in a 51–38 away win at Bristol Bears in the pool stage and a decisive late try in the Round of 16 against Wasps.

[18][19] His second season in France was cut short by injury, damaging his shoulder in defeat to Leicester Tigers in April 2022, which would prove to be his final performance for Les Jaunards.

[20][21] His contribution to the team was praised by coach Franck Azéma, who described how Matsushima "has speed, punch, he brings a certain execution in the gesture.

"[23] Matsushima made his international debut for Japan on 3 May 2014 in a 2014 Asian Five Nations match (which doubled as a 2015 Rugby World Cup qualifier) against the Philippines in Manila.

At the 2015 Rugby World Cup, Matsushima started in Japan's 34–32 upset win over South Africa, providing the assist for Ayumu Goromaru's try.

[34] Japan were eliminated by eventual champions South Africa in the quarter-finals, but Matsushima was named in the team of the tournament by ESPN and The Guardian, with honourable mentions from Sky Sports and Rugby365.

He is now one of the most influential athletes in Japan,[39] and his spell at ASM Clermont Auvergne in France was considered a sporting and marketing winning affair for the club and the city.