Hmm... well I just want to make sure, since I picked this set with the appropriate tag. Since the other two pictures are different in a sense (no similar background). Should this be in the "Touhou - Love Confessions in Gensoukyou" Pool or should I make a whole new one for Yuuka?

I'd say that if the others definitely follow on from this one, you might as well put them in the pool as well; there's precedent with a couple of other sets, most notably the Mokou set by Doombringer that starts at post #603105.

If it gets much longer, then it might need its own pool. For just four images where the start is definitely in Love Confessions, though, I wouldn't bother.

Give this man a trophy and be prepared to throw him the biggest party of the fucking century. He deserves it.