Kokubu started doing impressions when he was at a classroom sideshow in middle school.
When he worked as a salesperson at a precision instrument measuring manufacturer, he was joined with an acquaintance at the impressionist live house Sokkuri Tate Kisara at Shinjuku, Tokyo, this triggered him to start doing impressions on stage.
In about two and a half years after his debut at Kisara, he became a regular of Bakushō sokkuri monomane Kōhaku Uta Gassen Special.
Monomane Ōzakettei-sen: Saikyō Tournament Chō Gekokujō Special, Kokubu was placed first during his second appearance.
He continued to participate in Monomane Ōzakettei-sen, he won the final game for three consecutive years from 2013 to 2015, but he missed the championship.