So Yonji is a pretty curious guy, possibly the most curious of his siblings, so it’s natural for him to question where Reiju is when she’s missing. But when it comes to Niji here, I’ve noticed a few people seeing this panel as Niji being dismissive of Yonji and not caring about Reiju
But the next morning, Yonji asks Reiju where she was (perhaps not just out of curiosity but maybe also out of slight concern). Niji lightheartedly and teasingly tells him to mind his business and respect her space. So he was essentially respecting her boundaries and private time as a woman, and trying to avoid being nosy
Later on, Big Mom attacks Reiju and she’s knocked down. This does shake Niji, and he does show and voice visible concern towards Reiju here. So this leads me to think that he does care about her and was just respecting her space in the other two panels rather than being dismissive.
I guess what I’m getting at is that the Vinsmokes obviously aren’t a mushy family but they do care about each other in their own little ways