[Nyororin]

The conversation is backwards, the bottom is the oldest, the top the most recent.

I`m kind of undecided on whether it`s anything more than totally innocent flirting. Note that she HAS told the guy she has a boyfriend, and the whole thing is VERY heavy on joking/sarcasm. She`s laughing at him for the pretend shock about her having a boyfriend, which to me rings bells that it`s not serious. He responds that it`s not all pretend (a big *hint hint* type thing)...
I am curious what her response to that was... But really, I would not toss this in the cheating category. It`s a bunch of joking, really. If she were heading to Japan without her boyfriend, why tell someone she plans to cheat with that she has a boyfriend?

I am going to say 95% chance of just random joking flirty talk and nothing more.