From an idealistic point of view, a human is a human because they consider themselves to be human.
Suppose one day, there is a species of octopus.
They have their own language, their own writing system, their own education system, waiting for the update of "New Moe Octopus Anime" on weekends, flipping through mobile phones with countless tentacles, fantasizing about a creature called an upright-ape octopus, and existing in octopus mobile games as cute, moe octopuses while retaining the identity of upright apes.
Chapter 194