That was mental, in lots of ways. It might well be too bonkers for a general audience, but I was fascinated.
Firstly, it's based on a Key/VisualArt's visual novel, i.e. computer game. That's a bit like a fantasy gamebook with voice actors and modern graphics, with the only gameplay being multiple-choice route selection. Apparently this particular game's crazily huge, since there's a fan translation with over 100,000 lines of pure text. We thus have the question of what the hell this anime actually is. Is it trying to adapt the whole thing? (That would be mad.) Is it just doing one route? If so, is it going to melt our brains with the most apocalyptic ending available in the entire game, only to go back and do something completely different in Season 2? It's called "Rewrite", after all, and I think that would be a cool twist for a visual novel adaption. The Fate/stay night franchise has made an entire industry out of doing anime adaptations of different routes through the same game, after all.
Secondly, whoever did this adaptation has made some very odd choices. The first third of the season has something like a family-friendly equivalent of Tourette syndrome. It's full of comedy non-sequiteurs that lurch out of nowhere and get a throwaway reaction that's too brief to get anything from you but "huh"? If it does seem funny, that might just be your reaction to the surrealism. It's like alternative comedy that usually doesn't work, but I couldn't look away anyway. Sometimes I did laugh, though. (The unintended grope jokes are funny, for instance.)
The material's clearly crying out for more episodes and a more relaxed approach, but I don't have it in me to denounce a show that's being so uninhibited and weird. Theoretically Kotarou's early dialogue is similar to that of other leg-pulling Key/VisualArt's protagonists like Yuichi (Kanon), Yukito (Air) and Tomoya (Clannad), but the surreal delivery turns his jokes into something almost disorientating.
Then we have the show's content. It's a light-hearted school slice-of-life show with one male protagonist and various girls. (In the original game, I'm sure you get different routes for which one you want to romance.) The school uniform makes the girls look topless, even though they're not. It's all light and amusing... but this is Key/VisualArt's. Their first four visual novels were Kanon, Air, Clannad and Planetarian. Thus the story has some surreal elements underneath the normal school stuff. After a while this changes into lots of surreal elements. Eventually it goes completely apeshit. This anime has:
1. A girl with prehensile stabbing ribbon-limbs. She likes climbing into the bed of our hero (Kotarou) while he's asleep and biting his arm, then going away.
2. A knee-high mammoth that looks like a Pokemon and can head-butt dragons.
4. A magical forest.
5. Superpowers including a death touch.
6. A secret organisation that wants to save the planet.
7. A secret organisation that wants to save mankind from the organisation that wants to save the planet. Both of these organisations are altruistic, sympathetic and scary, having high-minded goals that are much more important than your life.
8. A gross blood-drinking flying dragon plant. Glowing wolverine claws. Homunculi. A theme of whether it's right to prioritise your friends over what should theoretically be greater loyalties, e.g. the existence of every human being on the planet. A love of horrible cheap coffee. A silly boob-fondling bet.
It's light-hearted, but also increasingly serious. Ep.5 is basically J-horror. There's a character who wants to see all mankind die in misery and has enough power levels to help make this happen a lot. It has a "you've got to be kidding me" ending. (They're not... I think. I need to watch Season 2, right now.) The show takes a few episodes to settle down and let the characters be themselves rather than Tourette's symptoms. (But not swearing.) It's got lots and lots of plot, but there's a point where I almost felt it was feeling a bit fragmented and/or mislaying its momentum.