You do realise that he wasn't in the mood to have sex and that people do react differently to same situations right? There was hesitation before he acted and knowing how stubborn Hozumi is, providing a more secure foundation of reassurance was the only way to comfort Hozumi at the moment, and it was the only way how. A man touching the body of the person he loves, will arouse him. A man looking at nothing will wake little Richard up, biologically, reactions happen, it doesn't mean that they agree with it. And at the time, he was frustrated he couldn't help, because he tried different ways to comfort Hozumi and the only way to get Hoz to look at him was that.
I think you misinterpreted what I said - I literally said that that it's to his credit that he looks less than eager. Because that means he had NOT gotten seriously in the mood to have sex from looking at his sobbing partner. (whether his dick reacted and he COULD do it is different from being seriously in the mood)

Well,that wasn't very romantic. Why does Yamato look like he doesn't want to be there? Is that his aroused face, cause i can't tell lol