Its first and most obvious flaw is that it progresses too fast. It is determined to set itself apart by portraying an attraction (of sorts) that's there and out in the open nearly from the get-go, but fails to recognize that this makes little actual sense when the characters hardly know each other. What is an attempt to portray, perhaps, a sense of naiveté or cute clumsiness from the male lead - both at this junction and elsewhere in the series - comes across as silly rather than profound. The way the female lead falls for the male lead and the attraction she experiences feels rather out of tune with the character established in the beginning, creating dissonance rather than actual development. The subsequent challenges they face versus each other and those next to them tend to feel forced and this is both a result of the unsteady premise and the fact that, well, it doesn't set itself that much apart in the end. The end is a little better, especially if you overlook the last twelve-and-a-half episodes, but just... no.
The other characters it portrays tend to be more of the same; unlikely and odd combinations that do not create interesting contrasts; rather, they left me dumbfounded at times with inane character interaction and stupid attempts at jokes. It felt... dumb. Simple and unclever. Few of the jokes really worked and their internal issues were driven by and challenged with equally plain methods. The ending was insufficient on many, many levels, failing to close some important knots and like so many other romance series, leaving the relationship itself a little too open.
Animation-wise it does not offer a lot. Character designs are probably its strongest suit and they appear rather average, with often-out of place body structure and simple shading (yet at other times especially shading and vividness is done quite well). The backgrounds don't mix well with the character designs and are often very simple, as are the camera angles and shots used. The soundtrack offers some nice string and piano tracks, but for the most part it is your run-of-the-mill romcom soundtrack with a mix of comedy and romance themes. The opening theme is a very average school/romance theme with the usual colourful backgrounds and animations we've seen a thousand times before. The ending theme is more flowery but equally bland in terms of originality.
Let this be said though. It avoids several common pit traps and clichés of romance anime, lacking both a distinct harem and many of the common episode settings that are so common. All in all however, Tonari no Kaibutsu-kun is an anime that tries to set itself apart, succeeds a little but eventually stumbles and falls face-first into the mud, void of any real sense of clever and intriguing writing. I did not like it at all and struggled watching through it. Maybe you have more luck with it, but I would not personally recommend it.
