Teppei can only come back to Hinamizawa if Rina gets killed by Rena or if her dad even meets her, basically. Reason being that Teppei's actions are done out of fear
When he moved from hinamizawa to Okinomiya, it was because satoshi killed his aunt, and Teppei thought he was next. With Rina, something similar happens.

Keiichi is supposed to be a "lackluster" and the fact that Rika got hope from a guy such as him is what makes it special. The final message is basically "tell your friends your problems :-)" but if you think about it, matsuribayashi is the only reality where they could of have succeeded. And yes, that means that happiness was only able to be achieved if everyone commited a "sin".

Keiichi disturbed others out of frustation
Mion and Shion were troublemakers as kids and that caused the tattoo incident to happen
Satoko killed her parents and lost his brother
Teppei is scamming people
Satoshi killed his aunt
Rika gave up on their loved ones
Hanyuu just dissapeared when things went wrong
And finally, Takano had a lust for success, even if that meant hurting others.

The final message is about that. Without pain, there is no happiness.
That there will only be joy, When They Cry.

Originally posted by dailyrana:

Teppei can only come back to Hinamizawa if Rina gets killed by Rena or if her dad even meets her, basically. Reason being that Teppei's actions are done out of fear
When he moved from hinamizawa to Okinomiya, it was because satoshi killed his aunt, and Teppei thought he was next. With Rina, something similar happens.

Have to clear up some points on that, so Rina doesn't have to be killed by Rena to come back. In Chapter 7, she gets killed by Sonozaki's family for stealing however she is planning on leaving Teppei regardless. So he does end up there and will due to money problems.

I understand the telling your friends point but parts of how Chapter 7 did things would of made the final world better. Since, a lot of "loose ends" could still happen. I just feel like parts which was detrimental to how these characters developed was kinda skipped.

Like Shion finding Satoshi which will stop her getting jealous. How Granny tells Irie to take care of both of them when they are said to be sick which stops the stigma of Hojo which was kinda lack-luster. How nothing happens about Rena's dad so it would be assumed he is still stuck in a slump, how Keiichi kinda doesn't overcome his paranoia and past to be a better person.

Again, I am not saying Chapter 8 wasn't the perfect ending but it just had a lot of looked-over parts which kinda makes it a bittersweet ending to me.

Oh yeah, absolutely
it was the first work of the author and it has a lot of not-so well written parts.

Gladly he learned from these and in Umineko, Ciconia and some other works this is fixed for the most part.