To be an asshole
pyeonghwa not wearing a condom seemed to be disrespectful/show his disregard for incheol's well-being on multiple levels, and then putting one on incheol after he didn't need it was adding insult to injury, something to mock him with. that's how I saw it, anyways.
The way I saw it, it was to not dirty Incheol's clothes ig? But the other answers make more sense
He was going to use one but bc people were outside and it would have made sound, he didn't. He reaches for it but then stops when people outside say they heard something. By the time he put one on incheol, they had left.
https://iweb_5.mangapicgallery.com/r/newpiclink/peace_of_god_mgs/39/f39c94e8af49c0a2c964e0d33e537c75.webp
I aslo thought that it is just to not dirty the cloths but then he again came on him. But how much noise coudl opening a condom make honestly. To me it looked like he changed his mind but why, i am not sure.
Youre answer makes the most sense to me.
I am re-reding it and does anyone know why Pyeongwha did not use condoms on himself but put one on incheol in ch. 21?