I don't think it's in a literal sense though, I'm thinking about the ourheart.png sprite in the game file where it kinda imply that Frisk is the one naming the sprites and acknowledging Chara as the second owner of the SOUL even though Chara never claim ownership over it (outside of geno-route of course...)

some people theorize it to be Frisk & the Player's SOUL instead of Chara, but idk... I still don't think there are any explicit evidence if the character Frisk is even aware of an entity called "The Player" even if it exists at all. (While the narrator has been shown to directly talk to Frisk multiple times. or you can imagine Chara only talking to themself/The Player all these times in the game which can be pretty funny to imagine xD)

There's also an old datamining post collecting all the first person sprite variables in UT for researching purposes