Kikuchi met Shields in a rematch in December 2004 and was victorious in a unanimous judges' decision, becoming the Welterweight Champion.
Following the route of training partner Norifumi Yamamoto, Kikuchi debuted in the K-1 HERO'S promotion in July 2005, defeating Katsuya Inoue by first-round technical knockout.
Kikuchi would secure another victory in HERO'S, overcoming a knockdown to take a decision over former Pancrase Welterweight Champion Kiuma Kunioku before returning to Shooto the next year.
Norifumi Yamamoto, a key member of Killer Bee, allegedly struck and verbally assaulted a Shooto official.
The official, who was examining a laceration on Kikuchi's face from the title bout immediately prior to the incident, appeared before the International Shooto Commission.