I thought that too or at least some passionate kissing
Sleeping the first time with your BF makes your Bond with him so much stronger, that Erika would not be able to function normally (even less than she usually does).
Also it was such an unspecial Situation. We probably see a bon, x-mas or living together situtation - or if any, lol.
What chapter did they have sex? Think I missed reading it
Chapter 54
I have to say this: why didn't they have sex in the last chapter? together, in the same bed, they already did it before, why didn't they do it again? why kyouya has to fell pain? (he says that it is painful..) or maybe they did it after that and the mangaka is not showing it to us... and I am a big pervert... ok.. I am going to whip myself for this. Sorry.