I will mainly write about why I love the scenario and characters and why I preferred the second part, the one which has never been adapted into anime. For this purpose, I am going to spoil the whole story, so don't read this unless you have finished the manga.

I moderately liked the beginning of the manga because I did not really understand what the characters wanted (the MC in particular) and it seemed to me that they were acting irrationally. The escalation of catastrophic risk taking was fine but not enough to make me love the manga and I think I was right because the rest of the manga gives a new meaning to this part which is in fact a mere introduction.

To me, it tells the story of boy who is introvert/asocial but not deeply abnormal and who cultivates his uniqueness because he fails to fit in. He believes that if he can't be as good as a normie than the other normies, it means he has a different/superior fate and he convinces himself that his "thing" is poetry, something the others can't understand. He finds a place for the pretty girl he fancies in this thinking pattern, calling her his "muse" (which is quite ridiculous). The MC is therefore at first pretty unhappy and lonely but comfortably confined in his simplistic relation with the rest of the world and vaguely in love with some girl he doesn't really know. This distance between them, which should be a source of pain, actually comforts the idea he has made of himself and make the situation more coherent and convenient than if he tried to seduce her.

When he gets closer to her, it is in fact natural that it doesn't go too well: he is still asocial, he doesn’t know how to fit in by her side and he doesn't have much to say to her. I hadn't understood it, reading the first chapters (I couldn't tell if it is normal, if we are supposed to understand later, of if I am a bit dumb, but however I understood later). On the other side, Sawa gives him an opportunity to increase his uniqueness, to improve his pattern which keeps him away from the others. She is genuinely different, way more than him, and even offers some new categories to add to his pattern (the concept of perversion, the concept of "shit-eaters" (misanthropy in fact) and the concept of "other side") which he tries to match with his understanding of Baudelaire's poetry. When he rejects Saeki to turn to his tormentor WHOM HE DOESN'T EVEN UNDERSTAND, I thought it was dumb, but it's actually very coherent. To this selfish interest is apparently added the desire to help Sawa, to offer her the company of someone who is like her and who can understand her, in opposition to Saeki who is a normie et doesn't need him. However, we clearly feel that he never completely succeeds, that she remains more special than him, that he never understands her and can't really save her, which creates a malaise during this whole part of the story which I find retrospectively delicious.

Then comes the chapter of the summer festival: she betrays him, pushes him away and tries to die alone. He doesn't understand, neither did I at the moment, but it's actually simple: she's thanking him for all these efforts he made for her which have mitigate her misery for a little while but wishes that he keeps living because she understood that he was less abnormal than her and that he could find his place in the world with some efforts, unlike her. The MC only understands this in the end and I only completely understood it at the same time he did. But what makes her so different? Why would Sawa be so desperate while he wouldn't? Is she right to think this way? She's right, and the reason is simple: as seen in the last chapter (which, in my opinion, was not necessary to understand this, but it is an indisputable confirmation which puts an end to any hesitation), she is genuinely, clinically crazy. I don't know anything about psychiatry but it must be some form of schizophrenia. Her perception of the world is biased, everything she says or do in the whole manga is irrational. She's desperately crazy while the MC is merely a bit different from the normies.

For some years, he won't get out of the illusion that he was different like her, that he was able to do something for her, and he will live in the nostalgic remembrance of their relationship and the incomprehension of Sawa's final act. It all changes when he meets the third girl whom he will seduce without giving up his particularity but without persisting in withdrawal. He will understand that he can be normal too, even if he has a passion apparently rare in his environment (literature), and finally give up his dumb pattern which was his shell during adolescence. Then comes my favourite passage: he meets Sawa, who almost didn't evolve, unlike him, again and, after a night of horseplay, reminiscent of the horseplay of their adolescence, she tells him not to ever come again because he is not like her.

I should also write more about Saeki and her friend Kinoshita who suffer a lot because of the MC's mistakes, they are two very good characters, but the essential point is here: a MC who doesn't fins his place and cultivates his difference; he believes (wrongly) that he can help a truly different (crazy) girl and persists in this way despite his failure without ever finding any satisfaction; it takes a lot of time for him to get over it but finally becomes normal while she remains in her desperate situation from which no one can get her out, and anyway from which the MC won't ever try to get her out anymore.