KO-D Openweight Championship
In mid-2013, Sakaguchi began feuding with the Monster Army stable, brought on by them stealing a gown and a statue belonging to his father Seiji. The rivalry culminated in an eight-man tag team match on August 17, during the first day of the Peter Pan weekend in Ryōgoku Kokugikan, where Sakaguchi, Akito, Kazuki Hirata and Masa Takanashi faced Monster Army members Antonio Honda, Daisuke Sasaki, Hoshitango and Yuji Hino. Sakaguchi submitted Honda for the win, following outside interference from his brother Kenji. The following day, Sakaguchi and Sato lost the KO-D Tag Team Championship to Isami Kodaka and Yuko Miyamoto. In late 2013, Sakaguchi was named the number one contender to the KO-D Openweight Championship, held by Harashima. En route to the title match, Sakaguchi submitted Harashima in a six-man tag team match on December 15 to win the Ironman Heavymetalweight Championship. On December 23, Sakaguchi failed in his KO-D Openweight Championship challenge against Harashima and, as a result, also lost the Ironman Heavymetalweight Championship back to him.