Rentarou is a kind, thoughtful, serious, and sociable boy who is easy to get close to. He knows how to study well and is relatively athletic.[3] Rentarou genuinely loves all of his girlfriends more than anything else, and is very easily impressed by their actions, especially when they do things that he finds cute. However, Rentarou is also very protective of his girlfriends and often needs to be calmed down should someone insult or harass any of them, hinting at a somewhat short temper. There have been times where he almost got into fistfights with people when they insulted or slighted his girfriends, or he feels that his girlfriends are in danger. Not only that but on multiple occasions he has displayed loyalty and isn't dirty-minded nor willing to do anything that his girlfriends don't want. He dislikes cross-dressing but does it for the sake of his girlfriends. “For the first time in my life, due to how big of a shock this one was...I thought I was gonna die from rejection.”

His favorite food is egg. Both of his parents are teachers. Rentarou, alongside with Karane, Kurumi, Kusuri, Kishika, and Suu are often referred to as the tsukkomi/straight man[6] of the group. Rentarou's birthday is on May 1st