So, yeah... it's not just that Soya's deaf- he loses his hearing randomly with no way to know when it will come back.
Also, yes, Rei is basically a teenage boy that's also a 'mother'. Hah. He's very caring, deep down. Hinata, in particular, knows this well. I figure she won't want to let go of him. I look forward to the day she reciprocates his dedication and loyalty to her.