Tanaka-kun might be narcoleptic. He hates unnecessary expenditure of energy, e.g. staying awake, eating, breathing. He's got the physique of an over-boiled noodle and about the same level of mental determination, except when it comes to stress avoidance. He's capable of forgetting what he was talking about. He's so pathetic that his best friend (Outa) often has to carry him from class to class. (Outa's big and strong.)
On the upside, though, Tanaka's also a nice guy and quite clever. He's a good observer of people, which makes sense since that's usually the limit of his physical activity. He'll acquire several friends over the course of this series and he's quite likely to say helpful, perceptive things that help get their issues in perspective and make them happier and/or less delusional.
It's a funny, likeable show. I'd recommend it.
The supporting cast is what makes it, of course. Tanaka and Outa are always fun, but Tanaka is an inaction hero and so the show needs a bunch of other characters for him to interact with. There are episodes all about Tanaka's efforts to avoid effort, but we also have:
1. MIYANO, who's tiny, hyper-energetic and super-enthusiastic. She's taken Tanaka as her role model and wants to be like him. This is so doomed. Just writing this paragraph made me remember Miyano and laugh.
2. ECHIZEN, delinquent and Outa's childhood friend. She loves cute things, so her brain melts when she's with Miyano.
3. SHIRAISHI, a fairly complicated character with issues. She's the one cast member who actually has real problems, whereas everyone else is basically just a comedy character. (That's not to denigrate them and I think it's a pretty good cast, but they are.) She's going to get interested in Tanaka, but that'll just be the source of a new set of difficulties and self-confidence challenges for her.
4. RINO, Tanaka's little sister. She's possessive of Tanaka and jealous of Outa. You might be getting worried at the sound of this, but fortunately she's just odd rather than incestuous. (Let's hope she stays that way.) She's also as deadpan as Tanaka himself and an amusing weirdo.
There are other characters, but those are the important ones. I liked them. They're lovable and they made me laugh. The only ones who are ever antagonistic towards anyone are Echizen (who's a sweetie underneath and doesn't mean it) and Rino (who very definitely doesn't want Outa around, but it's nothing personal). This is the kind of show where you could watch any number of episodes for ever and you'll be disappointed that there are only twelve of them. Hopefully they'll make more one day. It's an ostensibly plotless sitcom, of course, but there's character development with Shiraishi and maybe, a little, with Echizen.
The show's romantic side is sending mixed messages. On one level, the gay subtext can be pretty loud. It's almost obligatory in much of anime these days, after all. The audience expects it. Even leaving aside Miyano and Echizen, Tanaka and Outa is almost officially a couple. Outa might be big and intimidating, but all his traits are seen as feminine in Japan (loves sweets, shops like a middle-aged housewife, gets scared of things) and he's devoted to Tanaka to the point of attraction. Both he and Tanaka say on separate occasions that Outa would be Tanaka's ideal spouse. Meanwhile Tanaka is capable of describing himself and Outa as a married couple and of saying things like "I wouldn't mind giving my life to you, Outa". Meanwhile the show's most demonstrative mixed-sex relationship is Miyano-Tanaka and they both go out of their way to state that they don't see each other as members of the opposite gender.
Despite this, though, the text of the show is heterosexual. All of those four female characters I mentioned could be seen as potential romantic partners for Tanaka (although that would be a disturbing anime cliche with Rino) and half of them have shown explicitly that they wouldn't be averse to the idea. Echizen is in denial about being romantically interested in Outa. Shiraishi isn't even in denial re. Tanaka, although she has other issues instead. Meanwhile we know that Tanaka does actually have heterosexual urges and he'll be aware of things like boobs. It's just that the effort of romance would be utterly beyond him, while on top of that he's self-aware to the point of self-denigration and so thinks it would be rude to the woman for him to make a romantic move on which he knows he wouldn't follow through.
This's not a problem, though. It's a quirk. Sexuality is whatever we choose to read into this chaste, easy-going show and none of it really matters. The narrative has no opinion on who should be romantically attached to whom, except for being fond of everyone.
It's a nice show. It's relaxing and easy to watch. Obviously you'll need some tolerance for Tanaka, who in real life would be maddening and/or ill. Personally, though, I liked and was amused by him. This is a such a human lettuce leaf that he has to run away from puppies and even moving his facial muscles seems to be too much effort for him. I'm mildly tempted to go looking for the manga now.