Wait, did Akira have no response to her confession? He just sat there saying nothing, then they went home?
Rio plainly knows Akira's feelings for Asahino and is just giving him something else to think about before he makes any decisions.
I felt the same as
@outinthegardener. Akira's almost taunting non-response ("Nope.") struck me as strange and fucked up, though it may have been an effective PUA power move on his part. After taking a huge emotional risk and opening her heart to Akira, Rio clearly
wanted some kind of real, human-friend-like response from him. Yet Akira shut her down cold.
Note that this scene follows a set-up (see page 6) where Akira wanted to say something to Rio, but was unable to overcome his own cowardly indecision. Rio then bailed him out by saying what Akira could not.
It's a standard trope -- almost a rule -- in romantic shounen/seinen manga: the male MC never has to make a choice or take an emotional risk, and everything just comes to him on a silver platter. Annoying as fuck.