Sakura Chiyo is my favorite. She's has literally the cutest personality of any anime character that doesn't come off as annoying.
Mikorin is a close second. Just as bae and my face lights up everytime he's on screen. His drawing experience: I can relate.
Seo is also a close third. She's the best character of her archetype imo because I happen to hate inconsiderate bitch characters. She's the major exception.
Kashima is adorable af and she cracks me up a lot.
Hori-senpai is also a thumbs up. Same for Hirotaka.
Nozaki is one of the only dense characters that I like. I usually can't stand it when a character can't figure out there's a girl who just yells "Take me!" and he can't figure it out(Example being Satoshi Mochida, worst protagonist ever)but Nozaki being dense has a cute charm to it. I also like his attempt to be tsundere, lol.
So yes, the whole cast is great, but Tomoda-kun is the best one.