It's intentionally that way to simulate that they're being quite, that's why no one commented on it.
Viewing post in [OIHS] Only I Have Skills comments
I understood that - tons of VN authors do that - but when it’s so small that you can’t read it, it defeats the purpose.
If the MC had followed up with, “What?” to show that he hadn’t heard Pyrrhus, that would have been fine; it would have implied that he was being too quiet. But since he didn’t, it meant he was supposed to hear Pyrrhus.