@Sealight: He probably just did that out of spite or sadness, it's pretty obvious he is not accepting that girls feeling because he's interested in her.
Also, i'm surprised that so many people are already saying "Ship is sinking, get the lifeboats". For Sugawara and Takano, this will oviously not stop here, and for Erika and Ubukata, the fact that he's accepting to go out with a girl out of spite/sadness make it pretty obvious that we will see how it will play out. We only got only two volume left, yeah, but that doesn't mean we won't see them anymore.
(That aside ,Motoyama's ship have sunk, ok, but I'm pretty sure we will also get some sort of conclusion for him. And not necessarily a bad one)