A young teenage boy with ruffled blonde hair that almost reaches his ears and has red eyes. Seen as pretty handsome to others.
He often wears an orange hoodie under his standard school uniform.
"My life's goal is to create my two-dimensional bride!"
In the art club, he often draws 2-D 'waifu' and will always introduces his brides to fellow art club members, especially Mizuki Usami.
Despite his often irritating personality, Uchimaki has shown that he is a friendly person. He doesn't care what anyone else thinks of him even if they irritate or make fun of him.
As a member of the art club, he is skilled in drawing as shown when he got second place and later first place in the art competition. He is also shown that he can draw people who he only just met.
He was accepted on the Art Club despite his only interest is to draw the perfect waifu. He pass all the time in the club doing it and when he asks to Usami or somebody to be a model to his drawings, he makes it totally different or adds some cat ears and tails. Uchimaki does not perceive that Usami loves him, so when she is nervous because of some situation about him, he thinks she is kidding or just being weird.
She is also a club member. Mizuki has a crush on him but Subaru does not seem to possess feelings for her although some clues in the anime and manga seem to point out otherwise. In the anime in episode 12, Subaru wants to call Mizuki by her first name only because his favorite character had the name "Usami" and did not want to mix up the two, although, this doesn't really mean that he has a crush on her.
In many episodes, whenever Imari was here, she would notice the two having the same wavelength and being totally in sync.
In episode 6, when Subaru won the art contest, he wrote Mizuki's name alongside his saying that it his and her effort combined that made them win. Also, in the same episode, when Mizuki came to the clubroom discovering Subaru had put his uniform and tie in the sofa, she put them in the closet. When she did, she said, "I'm not your mother, Uchimaki" and then Uchimaki replied "True, age-wise. Then, you'd be my wife I guess", thus showing a little hint.
- He planned to quit the art club early on but didn't. He claims this because he wasn't completely satisfied with what was supposed to be his final "bride", but decided to continue immediately after seeing that Mizuki Usami would be lonely.
- His zodiac sign is Leo.
- He resembles Nagisa Hazuki from Free! and Asahi Kasumi from Aikatsu Stars!