The headphones

i was doublechecking if they had double ears the artist sure didn’t twice before drawing them

didnt think twice**

I think the headphones are made with downturned ears and upturned ears in mind, like one applicable model for everyone

The author actually explained something about that in the heat x beat 1 manga by the end of chapter 7. Well, that's just how they try to convince themselves. (Vestigal something)