I think I finally figured this one out.
Although it's obvious, it never really clicked with me that they're hanging their clothes to dry *outside* and the discussion about underwear theft isn't just idle banter, but an actual concern that some of Haruhi's panties might go missing.

It also didn't help that in the first panel I mistook ナニ for 十二.

Well, you also mistranslated the punchline, unfortunately. Fixed.

I can't unsee that punchline..... FFFFFFFFFFFFFFFFFFFFF

NightFoxXIII said:
I can't unsee that punchline..... FFFFFFFFFFFFFFFFFFFFF

same

I just pictured Kyon in that and... actually, I'm not really disgusted. Good taste, my man.

I...never thought of it that way before...

Maybe he meant "his" as in he bought them for Haruhi to wear.

Calando said:
Maybe he meant "his" as in he bought them for Haruhi to wear.

Nope. Kyon literally says that the thief may not know whether he's taking the ones Kyon wore.

...and picturing him in them is making me laugh hysterically.