Yeah... Pretty sure this isn't that kind of manga- these two are basically staying together, and any troubles are going to be short-lived. That's pretty much how it's more or less been from the start, and that's how I see things being going forward. Shit might get more serious, but there will always be the end-game of Kyoko and Izumi being eternally bound. Their relationship started because they spent about a whole year hanging out at her house being like the parents Souta deserved until they just couldn't deny their feelings for each other anymore. Those sorts of romance stories don't really just end in tragedy.
Hell, the anime ends with Miyamura basically monologuing that he'd gift her the sky if he could at graduation, and they're clearly still happy and together there.