The Brazilian-Japanese lightweight, who submitted previously unbeaten Adam Piccolotti in September, has signed a new long-term deal with Bellator, MMA Fighting has confirmed with the promotion.
Yamauchi has gone 3-0 in 11 months since moving up from featherweight, scoring first-round submissions over Piccolotti, Valeriu Mircea and Ryan Couture.
The 24-year-old talent signed with Bellator in 2013, and won five of seven bouts at featherweight before going up to 155 pounds.
Bellator has yet to announce his next fight.
Speaking with MMA Fighting prior to his most recent bout, Yamauchi explained why he decided to go up to lightweight.