It's a harem show and often silly, but charming.
Kimito Kagurazaka has been kidnapped and is now the property of All-Girls School Seikain! (They were misinformed about his sexuality and they think he's only interested in male bodybuilders. If they learn the truth, he'll be castrated.) His new classmates come from families so rich that they're full of curiosity about these strange alien things called "commoners" and they don't seem to have ever experienced films, TV or mobile phones. The school's worried about this, since for some reason their students have been known to crash and burn on hitting the real world after graduation.
Their solution is Kimito. "Shomin" means "commoner". Kimito's job is to be to the Sample Commoner, as if they're deliberately giving the students a virus so that they'll develop immunity.
It's a daft premise, made sillier by how far the show's willing to take its girls' naivety. Aika, for instance, will believe anything. Just say the magic word "commoner" and she'll deactivate her brain and eagerly do the most stupid thing you could tell her. Kimito will deliberately test this for laughs, but he still hasn't found any limits to it. However that's basically true of the whole school, who'll be sent into raptures by ideas like self-service burger joints, instant ramen and maid cafes. Kimito in ep.10 makes Aika dress up as a Japanese comedian and say his catchphrase. You could even identify a formula to this. The show will introduce the girls to something from real Japanese culture (which could be either mundane or cringeworthy), whereupon they react with awe and start practicing it.
This is ludicrous, but also often very funny. Unsurprisingly the girls are all fascinated by Kimito, so before long he's acquired a fan club. (They call it the Commoner's Club and it's an official school organisation. Its members are Kimito and four girls, who hang out together in his room and discuss commoners.) This makes it a harem show, but fortunately it's a gentle one without a sexual angle.
One thing I really appreciated, incidentally, was the fact that the harem angle is plausible. All too often in anime, it isn't. Here, though, it would have been strange if these girls hadn't been fascinated by Kimito, like stamp collectors who've seen a Penny Black. Besides, none of this ever turns sexual and the show would have been almost unchanged had Kimito been female. Everyone's obsessed with him because he's a peasant. The fact that he's male is of very little interest. Admittedly the show's main girls will all end up fancying him, but:
(a) they wouldn't recognise their own sexuality if it walked up and bit them, and
(b) if Kimito ever stops being a de facto girl, he'll get his gonads cut off. Basically it's a show where everyone's all friends together. Well, except for Aika and Reiko.
Running through the cast...
KIMITO - usually a nice guy, but can be a bastard when he sees an opportunity to troll Aika. Has a creepy thigh fetish, although fortunately it's only rarely glimpsed.
AIKA (orange hair) - avoids her classmates because she knows about (some of) her own personality flaws and she's afraid of saying the wrong thing, but she also wants to be popular. Sees commoners as almost supernatural and herself as Kimito's disciple.
REIKO - the only girl who could pass for normal, in a bad light, if you didn't talk to her for too long. She's beautifully polite and ladylike at all times, except for some reason when being antagonistic towards Aika. That's mental, even by this show's standards. Every so often they'll say they hate each other and be a bit snippy, but in practice they're quite nice to each other and I don't think anyone really believes that they're enemies.
HAKUA - probably autistic. Avoids human interaction, almost never speaks, is fiercely attached to routines and is liable to go into trances in which she strips naked and starts scrawling mathematical equations on the nearest flat surface. She's a mega-genius whose calculations could revolutionise science, but that's hardly incompatible with autism either. Even her physical development is arrested. She's about fourteen years old, but looks six. (Thus her nudity isn't taken seriously and Kimito simply laughs it off as an obvious joke when someone tries to tell him Hakua's age.) Theoretically she's the token mini-moe character. Lots of harem anime have one. They're meant to be cute. Hakua isn't in any conventional sense, because she's clearly handicapped, but she also grows somewhat on acquiring friends and becomes capable of breaking her routines.
KAREN - samurai girl, possibly mad and certainly irrational. Is fixated on being a stoic, gruff, macho warrior, but doesn't seem to have realised that she's a shy, delusional, needy, tsundere, easily embarrassed girl who's obsessed by cute things. This is funny. She's less troubling than Hakua, because she's clearly functional on a day-to-day level and indeed is usually competent and useful. Example dialogue: "Where is there any proof that the me who is here is really me?"
One could even hypothesise that the school isn't just a school, but an institution for rich girls with certain psychological conditions. Hakua's facilities in particular could almost be a hospital with carers. This would cast a new light on the season finale, in which our heroes try to prevent an arranged marriage because they want the girl to choose for herself and be with her friends. If everyone at the school really does have problems like this, then that would become a bigger deal than it looks. (At the time I was doubtful about whether our heroes were doing the right thing, because getting married off would at least mean graduating from Kimito's harem. Staying glomped on to him like a leech and deluding yourself that he's yours and no one else's can't be good for long-term mental health.)
The finale doesn't really resolve anything, though. This show is based on a light novel series and they're actively trailing a Season 2 that I'm not expecting to get made. (We never learn what's going on with that Kimito-hating head maid, Kujo, while the series ends on a coda with a newish-character, Kimito's childhood friend Emi.) It's not a bad finale, mind you. It raises the stakes enough to make its drama a bit more meaningful, but then afterwards it's back to normal again.
There's some fanservice. It's not serious, but the school uniform seems to have slightly transparent skirts and there are occasional panty shots. Karen also has a clothes-stripping sword attack, although her victim usually ends up being herself.
Is this a realistic show? Hell, no. However it has internal consistency, once you've accepted the premise, and I could usually believe that these characters would be like this. (The school headmistress can sod off, but she's only rarely glimpsed.) I enjoyed it. I laughed a lot and I think it's much better at the "super-rich students being amazed by mundane objects" gag than, say, Ouran High School Host Club. It's also a harem show where the harem angle is relatively downplayed and only a minor source of gags. I'd like to watch more of this. If they made Season 2, I'd be on it like a shot.