three ;
[Sakura is certainly not the type to be prying into other people's personal thoughts, but it's a little hard not to stare for a moment while the bubbles appear out of thin air. Much as one may be used to the strange events happening here, that sort of thing was always curious.
... Moreso when the bubbles keep piling up. It takes her a second to realize maybe the person they're coming out from hasn't yet realized they're there.]