It's natural he doubled down tho: Kang has ALWAYS been left by those he was in love with. Going through this time and time again will make it natural for you to expect nothing else. Especially not from someone younger.
It does not have anything to do with him not wanting a lasting relationship, it's simply what life has taught him to be normal. hence his words/thoughts/feelings.
XD I have had that desire many times too! They should definitely implement that feature. Just a small heart emoji in an upper corner would do it for me.
Couldn't agree more with you btw. Kang is, in a way, just as inexperienced as Yiyoung. Which is something that could bring them closer together at some point. Or so I hope anyway. (T∇T )

No way he doubled down. Imagine telling your partner you don't see each other staying together for long then not even understanding why that's a terrible thing to say. No winning either because they either break up when they're still in love or you're stuck with a guy who's not even in it for the long run