Coach Massimo Ficcadenti decided to use him from the first league round and, at the end of the season, Muto reached 33 appearances and scored 13 goals, matching the top debut record in the Japanese first division.

[11] Premier League club Newcastle United announced on 27 July 2018 that they had reached a deal to sign Muto, pending him being granted a UK work permit.

[12] He was granted the work permit on 2 August, officially becoming a Newcastle player on a four-year contract as part of a £9.5 million fee.

[16] Muto made his debut for Japan on 5 September 2014 in a 2–0 friendly defeat to Uruguay at the Sapporo Dome, replacing Yusuke Minagawa after 58 minutes.

[18] As a substitute, Muto played all of Japan's matches at the 2015 AFC Asian Cup in Australia, ending with defeat to the United Arab Emirates in the quarter-finals.