So let's briefly break that analogy down. Some people are into things that most people find unpleasant, primarily because of that very fact alone: It's considered unpleasant. But getting through it, and finishing it, is the point. To say you experienced it is the point. Some call it counter-phobia, or doing things one finds fearful because there's a high after it's done.
School Days is a lot like that. You don't really watch it for the enjoyment of watching it. It's not even meant to be enjoyed. Its characters aren't supposed to be likable, the events aren't supposed to make you happy, the choices made by the characters are supposed to get under your skin.
But by the end of it all, you still feel better for watching it. This is a deconstruction of the harem-romance genre, and it's sort of a giant pair of middle fingers by its creators to the people who do like them. The writers know the characters are one-dimensional, they know the main character is loathsome, they know every other character is just as loathsome for many reasons you're welcome to pick out, and if there were such a thing as the creators having hate-sex with the audience, this is pretty close to the idea.
But for all the unrestrained hatred for its characters that you do have to tolerate just to get to the center of it (which is really the last three episodes, the last one being an exceptionally-delicious punchline to a 12-episode running joke about harem anime), it really is an experience to remember.
Granted, the first half of the anime is about as average, tame, and innocent as it gets. Seriously, it's every harem trope thrown out there ad nauseam. Then comes the part where the creators take all the characters and situations they've set up and violently, sadistically tear it down for your entertainment, culminating in a, "Oh. Oh, that's...That's not right. That's not what's supposed to happen to anyone, ever." nausea-inducing climax.
You may or may not appreciate the point of the anime, but if you think you can appreciate the idea of a generic harem anime straight-up switch genres into a horror anime without skipping a beat, this is your thing. If you can believe that sort of thing might work, School Days does it, and it does it rather gracefully, without you even really noticing it while it's happening until the whole thing quietly activates its self-destruct sequence.
Oddly enough, the most horrific part of this anime actually has exactly zero violence or really any action of any kind, and involves nothing more than a girl reading a text message and her subtle reaction to it. It's an astronomically cruel and soul-ripping text message that is somehow worse because it *isn't meant to be cruel at all* (the one encouraging her to...you know, go here and get this taken care of, for her own sake, and it's sincerely meant), but considering the emphasis on text messages in the show, I suppose that's rather appropriate.
This is ultimately for horror fans, definitely not anyone look for a lighthearted school romance (which is totally how it's supposed to look at first). Don't even think about watching this if you're not a fan of horror and tragedy, because that's what it ultimately is.
"The party you are trying to reach is not available at this time..."
