Ryuutaro's reaction wasn't easily classified as a specified feeling. For one he was a tiny bit amused, but then again he could never approve of such disgrace being brought upon Hayato caused by anybody else.
His mixed and mostly negative feelings about families right now were stumbling around above each other.
"Seems like you had a lot of fun", he commented out loud and it could basically mean anything from 'How dare you do that' to 'that day history was made'.
Ryuutaro didn't exactly feel like being more personal so he kept up a basic smile.