Sephiroth would be easy to find in most crowds, even without the less mysterious than Cloud thinks connection between them. That said, just because he's easy to spot doesn't mean it's instantaneous. Cloud may be surprised and gratified to find that Sephiroth is...actually lingering on the fringes of the party, seemingly people-watching, looking - not perhaps outwardly uncomfortable, but at least out of place. It may be incredibly familiar and relatable to Cloud.

The number of similarities the two of them have is probably going to be a perpetual surprise to the blond.