Yeah me too, i felt like barging into that scene and put someone in a timeout
I think this behaviour suits him even in sex because he was always reluctant to do romantic things but also deep inside of him there was a part that want to do.. But this is just an interpretation
What you said fit chiwoo perfectly but relunctant does not equal it hurts. For me it would be more "no, stop, dont" you know the usual uke does in other manga.
Also it could be that he's relunctant like you said, just that it was used a bit too much. Both scene contain a bit too much of "it hurts" it made me cringe so bad.
The sex scene kinda bother me.. it was hot yes but just that chiwoo kept saying it hurts makes me cringe badly (￣∇￣")
Hot and hurting doesnt mix together. U keep wanting to enjoy the smut but at each turn he keeps reminding the seme that he's hurting....