Who will he alter first ?

Everyone, with a slight cavet.

John thought it would be a good idea to involve everyone. Afterall, good things need to be shared, right?

Before snapping his fingers, he had the idea that everyone would be hyper sexualised in regards to seeing each other. It didn't matter who. Once a person laid eyes on another, the need to strip, on part, or fully, would commence and ultimately lead to some sexual circumstance.

But what differed here was people would still have their old thought values from before. Mentally, they would abhor it. But physically, they would do it.

Let's get this ball rolling shall we?