Oh, the whole Omori x Sunny dynamic is such a fascinating topic! While the game 'Omori' leaves a lot of room for interpretation, I wouldn't say it's explicitly canon. The relationship between Omori and Sunny is deeply psychological—more about self-reflection and trauma than romance. The game's surreal, dreamlike narrative blurs the lines between reality and imagination, so shipping them feels more like fan-driven headcanon than anything confirmed.
That said, the fandom has run wild with the idea, and I totally get why. Their bond is intense, almost symbiotic, and the emotional weight of their connection makes it easy to see why people would ship them. But if you're looking for official confirmation, you won't find it in the game itself. It's one of those things that thrives in fanart and fanfiction instead.