Ryouichi Aizono

Issei and Ryouichi are cousins and have been inseparable since they were babies — now they even work at the same company. Compared to Issei, Ryouichi is quiet and does everything Issei tells him, to the point of annoying Issei, who assumes that Ryouichi envies and wants to copy him. [Spoiler] Ryouichi adopting the pseudonym "Shimizu" — thereby distancing himself from the Aizono family they're both part of — may be a hint that he is being truthful when he tells Issei that his obedience comes not from the desire to copy him, but out of his love for him. [/Spoiler]