I'm not sure if there is even any sort of proper etiquette for this, so you can say what you want. Even if that means not replying at all.

[For what should he even reply? Ryuutaro knew that Hayato could not give this back, but that was fine... at least for the time being. Ryuutaro knew the anti-social way he lived was exceptional, even if he was getting better. He had people who he got along with, but he wasn't just ready to properly call them friends.
And that was fine, he never wanted any. He was like this because of his own choice.
Hayato wasn't like that, he'd almost painfully seen that. And if he needed acceptance and being liked than it was like this.
If Ryuutaro was in a good mood he didn't care. He was not that possessive.]