I've read all over the seemingly many topics about how to get over the game. As this is maybe a little help for you, I will try to clarify things, in order to discuss and help each other - this will as well be my own attempt on getting over it - again... So please do not post things like "olol I had no probs" as they will be ignored anyways by people who seek help. And yes, I registered just for this one.
So I've read Hanakos arc (good ending) - and I got similar symptoms some of you had:
1. The urge not to play another path, because it would feel as cheating
2. The wish to experience something like that yourself
3. The feel of losing something, sadness after the path (which is not to be confused with being touched because of a romantic ending)
4. The feel that you can't complete the route or the game, because then, (like someone around said earlier) there would be "no more" of the girls
So I am not going to boast or tell you how much of an experienced person I am or whatever (because that obviously makes no sense in a forum full of anonymous people), but let me tell you that I have read quite some VNs in the past - all of them were VNs heavily based on the storyline instead of h-scenes. And the phenomenon of the 4 points above are not exclusively appearing in KS - they are gonna happen (more or less) in every decent to well written nakige (crying game). So I played quite some of them, including Clannad, Sharin no Kuni, Crescendo, Hourglass of Summer etc etc. And some of them let me behind, up to 2 weeks I was deeply saddened, and quite often on the verge of crying. It was a deeply hollow feeling, feeling a pressure on my chest that made breathing a thing I had to do actively, including the above mentioned feeling of loss. Since I experienced this a couple of times now, and I had time to analyze myself, I think that I at least could get near the core of the problem.
And yes, you are right when you say that some of them are not genuine romance-based games. But: They all have something in common: You are going to start a relationship with the girl you like. And thats the point! It is not important if you play an adventure-based, fighting-based, sports-based etc. game, including minigames or whatsoever, as long as you are going for the girl you like in its progress, and finally get a relationship.
So. the problem is not, that you play such a game - because, as I read here before as well playing it feels kinda nice, uplifting, entertaining and, for some, relaxing. Yes, some of the stories are deeply touching, sad etc. But that does not bring up the 4 problems - such sad stories can be found in movies and books as well, but I don't think that anyone would feel like above because of them. The real problem is when the game ends! Only then do you realize one thing: Because the game ends at a certain point, there is no more line to read, no more expression to see, no more dialogue to start, and no more relationship to have. The girl you started your relationship with, now dies. In a metaphorical meaning, but it feels just like that. You are not gonna get in touch with her ever again, read just one line of her thoughts. Notice that these symptoms and feelings may be stronger for one reader than for another - for me, they almost every time busted me completely.
So the real problem seems to be that you became... well... happy while building a relationship, not knowing how it will turn out, being full of excitement and hope. Dealing with your girl, you come to like her (some even write love), although you absolutely know that "your girl" is a character which was born in the creativity of a writer. As long as the story is there and you still have lines to read, you don't (or don't want to) realize that. But after completing the arc, it strikes you. While playing, dating, protecting, flirting and witnessing the progress in your relationship, it seems that you produced a huge load of serotonine ("happy hormones"), which you produce as well when dating a real girl irl. But while your real girl does not disappear, and you enjoy your relationship, this flow abruptly ends with completion of the vn, and what follows, is withdrawal (is this the right term? i am not a genuine english speaker). Thats what I meant with your gf dying.
All four symptoms are explainable by what I said above:
1. Because you really like your girl, you can't cheat on her, so you can't just go over to the next one to get the next happyness-dose.
2. Now thats a tricky one, because it needs you to realize, and more important, accept, that your girl isn't real. Realizing this is easy (because you can still make rational statements), getting over it is much harder. This explains such statements as "in a relationship with x" in signatures of some of the users here.
3. This one is largely explained above. Most well written VNs let you forget that you are not the protagonist (by forms of narration, first person opinions, thoughts etc.) and let you forget or ignore that it is fiction. This is hugely supported by nice-to-look-at visuals and (especially for me) well written bgm.
4. This is the result of the one who started to think about his sadness. He wants to save some lines for later, knowing that it will end soon. He wants to be able to tell himself: "My girl did'nt fade away yet, I have some happy hours left to spend with her. As I know that it will eventually end, I take the serotonine doses which are left and go for a slow detoxification"
So what can you do about it? I tried many things, and their potential of helping you depends on how hard it hit you. Heres what I tried:
1. Getting out to do something else with friends. This one needs friends, because if you are going out alone, you are very likely to be outside, but remain sad. When you are going to do something with friends, do something that keeps your thoughts busy, not letting yourself be lured into thinking again. It is very hard to even feel a bit better if it really hit you hard, pulling only down your friends' mood as well.
2. Playing another arc. IF you don't care about problem 1, you can try that, but remember: There is no guarantee that it will make you better after completing the next arc - maybe this one leaves you more depressed than the first. If you just keep going, you eventually reach the end of the whole game, and then theres nothing left, and you have no more to read. This happened to me and I was at exactly the same point like before, not less sad, and out of anything that relates to the characters. Furthermore, while you approach another girl, you will see your "old" one, talk to her etc., and this really, really hurts.
3. Playing the same arc again. Torturing! Because seeing your girl that does not know you anymore, doesn't like you yet is like having her memories erased. For me, absolutely no help!
4. Playing another vn. This is a better one! And it helped me in the past. You don't see your old girl again, and theres a whole new world introduced to you. But hey, you may think, then I'll complete that one and feel like shit as well! You are right! And because of that, you don't finish it! The problem here is that you can't do this with a "good" vn, because then you simply want to read on, and fall for the trap. It has to be a vn that is funny and does not push you into a relationship fast. An example may be the first chapter of Little Busters. It is funny to read, you get "in touch" with new characters, but it keeps being superficial a long time. You are trying to "bore" yourself out. I am not saying that Little Busters is a bad game, but the first chapter is just playing around, and not getting involved with a girl too deeply. Another example may be the beginning of Edelweiss. Its so stupid, you wanna run away.
Because of that, this solution combines several advantages: You have the feeling of still having some (or a lot) of lines to read, you don't see your former gf's sad face and nevertheless get at least a little bit of your serotonine, because you know that there COULD BE a relationship if you wanted - because even funny vns get serious at some point. What is crucial is that you dont want to go too far, get too involved (notice: you can restart the game anytime you feel better, theres no need to play it through the end NOW just because you bought it). So you have to stop yourself from playing at exactly the moment when you think: this is funny, but there could come some deep relationship now because otherwise it gets boring. Don't let yourself be fooled by the story - the beginning of Edelweiss is just "funny" trash, but after that, there is one of the most depressing routes I've ever read waiting for you.
This way obviously has the problem that you actually have to own a vn that you can read.
5. Looking forward to experiencing all of that yourself. Yes, it may help, I think. A bit, because, like it was mentioned, you have to accept that this girl is fictional and has an ending, although it was "your" girl. Furthermore, you have to be in the situation that you still go to highschool and are able to experience something like that. This is one of my big disadvantages - I am too old and out of highschool - but lots of vns focus on that topic, you being a student in 2nd or 3rd year and stuff. I can't possibly experience that anymore in my life, and because of that I can't look forward to it.
6. Writing on forums like this one. Yes, it helps, a bit. It is comforting that you are not the only one experiencing this. Someone compared this to meetings of alcoholics talking abour their problems. Well, I think it is not too far fetched. Because of this I wrote this to help you, and of course would like some replies as well.
So, to summarize, only 2 of 6 ways helped me a bit. If you are a sensitive person who tends to be too emotionally involved too fast, my best advice would be to not play vns anymore - it will only bring you suffering in the end. It is like paying with a huge headache for your drinking and having fun last night - only worse. Why I can't follow my own advice? I seriously don't know.
I hope I could be of any help to some of you who are suffering, and I am looking forward to a constrictive discussion, or simply your thoughts on all this.
Thanks for reading all of this, but you can imagine now that I have had quite the time to work this out