Yamauchi made his professional debut against Supaluek Noiwaengphim on 30 June 2017, whom he beat by a second-round knockout.

[5] Yamauchi was scheduled to fight Wulan Tuolehazi for the vacant WBA International flyweight title on 30 March 2019.

Yamauchi suffered his first professional defeat, as Tuolehazi won the fight by unanimous decision.

[8] Yamauchi was booked to fight his fellow countryman Satoru Todaka for the vacant WBO Asia Pacific flyweight title on 19 August 2020.

[13] Yamauchi faced Josuke Nagata for the vacant Japanese flyweight title on 1 April 2023.