In May 2020, Tachibana founded the Horiemon New Party. Tachibana named the party after entrepreneur Takafumi Horie (who was given the nickname "Horiemon" due to his resemblance to the manga character Doraemon) and uses Horie's likeliness in campaign ads. Despite this, Horie has publicly stated that he does not have any connection to the party and that Tachibana used his name and likeliness without his permission.
