"Oji-san no pantsu...?" isn't a typo.
In the Japanese version of the game, Hoshino refers to herself as oji-san.

kirbylittle said:

"Oji-san no pantsu...?" isn't a typo.
In the Japanese version of the game, Hoshino refers to herself as oji-san.

So would "This old one's panties?" be a better fit?

Went ahead and fixed both bubbles, the second one seemed to have been read as "そんなに" where it's "そんなの"