I think that the significance of this shot, showing Kakyoin waking up, is both him realizing that he just technically had a sleepover (likely his first) at a friend’s house, and realizing that he has people that care about his general well being. He’s in a nicely prepared room, with what appears to be a cup pitcher of water and a note (?) behind him.
His forehead is carefully bandaged, and his earrings are neatly put away as well.
I’m sure after months of Dio controlling and invading his thoughts, it’s a nice respite for him to just be able to lie in silence and contemplate the events of the previous day.
It’s a really subtle addition, but I’m really glad DavidPro decided to put something like this in, because you can only really appreciate it after learning Kakyoin’s backstory.