Those kinds of speech bubbles (thought bubbles) are also used for whispering. Normal bobbles with dotted lines instead of solid lines around them are also used for whispering.
You've become quite captivating!W...Sorry, I can't really tell.Well?Have I slimmed down a little?That's right... we never really measured her weight or anything.Sister, you dummy.You look lovely, Lady Patchouli!Y-You think so?!That's my Sakuya!
