Eikichi is a flamboyant student of Kasugayama High. At a younger age, he was overweight and frequently bullied. After a thug pulled down Eikichi's pants in front of his childhood crush, he underwent a radical image makeover, losing weight and training to beat up anyone who mocked him. Eikichi was capable of summoning his own Persona before Tatsuya and Lisa. Like Maya, he misunderstood the phenomenon and dubbed his Persona a "Spirit of Death", which he used to punish anyone who challenged him. This acquired him the nickname "Death Boss" — parodied by some as "Undie Boss" — and resulted in Eikichi becoming greatly feared and admired within Kasugayama High School. He is a true narcissist, always looking at his hand mirror and praising his own reflection.
Eikichi is also the lead singer of a rock band called Gas Chamber, whose logo he wears on his armband. The group consists of Eikichi and three of his friends, each of whom refer to him by his stage name, "Michel" (an abbreviation of his surname). Though none can play instruments, Eikichi believes that the band will achieve fame through his vocals alone. They have composed one song, entitled "Luv Beam".
Eikichi's weapon is a concealed machine gun shaped like a guitar case. His initial Persona is Rhadamanthus, and his ultimate Persona is Hades. Eikichi wears makeup and dresses like a visual kei rock star, despite the impending fear that his traditionalist father would punish him if he knew. (It is stated that his hair is not permanently blue as depicted in his artwork; he dyes his hair every day before going to school.) He wears a modified version of Kasugayama High's blue uniform, with a tunic over his pants.