The characters aren't particularly unlikable but they aren't really that likable either, they're a bit silly but pretty average overall. I thought Mai was despicable, always being dead serious and "winning" any situation she was in. It felt to me that she was trying her best to act as cool as she could, at least that's what it appeared to be to me, and I hated that. Another I hated was Shinonome. I can't exactly call her an asshole, a bad person or irresponsible (since she's a child it's pretty normal) but she messed with Sakamoto and Nano in nearly every scene she appeared in. Seeing a robot girl crying and scared of how her body was designed and asking to be normal while her creator is casually cheering that it's cool and she can store food inside her arm isn't something I find really funny and it's a running gag to boot.
All that is left for this anime is comedy. You might as well save yourself some time and search for the funniest/best moments on youtube. It also does not have much rewatch value imo unless you want to show it to your friends to see their reaction.
