Kyon...he's...he's apparently very good at holding his mind in check while he's getting a blowjob and close to going off.

He could half be doing math homework during Kyonko's ministrations with this sort of thought-separation.

Translation nit:

> Ah, this idiot kept his panties on

Presumably this is the same as Japanese ぱんつ, which should be "underpants" for guys. But I don't feel very good about correcting Korean since I haven't learned to read hangul… yet.

I think it's funny calling them panties, translation accuracy or not.

So wait, why can't Nagato find out that he's been masturbating? I can't imagine she would care, or that Kyon would be embarrassed about her knowing.
If this were any other doujin she would be helping him out herself.

just as a tip

Panties in Jap and Krn both just mean underpants whether if it's brief or boxer, even female panties in American (or any) culture.