Sasuke is a weird sleepy kid. Hibiki is worried about him because he doesn't seem to care about himself at all and that's obviously no good. They haven't talked too much yet because of Sasuke's condition when he arrived in Hirajiro, but he kind of gave him that "this kid won't open up easily" vibe. Mostly because Hibiki's similar about opening up, haha. It's okay though, these things take time...

Or, well, you can always have a shadow just spill the beans (: