Also known as: 麦刈公一, Mugikari_Kōichi
Koichi Mugikari is a primary ally featured in the Ma Shounen Bt series, as well as its one-shot pilot, B.T. "The Wicked Boy".
He is an ordinary boy who befriends the malicious B.T. and tags along with whatever adventure the latter has.
Koichi makes a return in the spin-offs Cool Shock Old B.T., Cool Shock Guy B.T., and Cool Shock High School Student B.T., which follow events in B.T. and Koichi's lives after the original series. An alternate version of him appears in the 2024 reboot manga.
Koichi is a young boy of lean constitution. He has a lean face, a small pointy nose, oval-shaped eyes and tear-shaped eyebrows. He has dark wavy hair, cut into a regular haircut. In the reboot, he wears a hoodie that says "echoes".
In the Cool Shock Old B.T. one-shots set decades after the original series, Koichi has become an old man. He is rather short and stocky. His hair has whitened with age and he's kept the same haircut from his childhood, but has now a short beard that leaves a large patch unshaven around his mouth and is split between the nose and the lips. He wears a suit with a tie to which he adds a pullover. His jacket is a plain jacket with vertical stripes with clear and slightly darker stripes.