The only preposition you could properly use here is "in". To understand why, you need to understand what that part of the sentence means -
It arises from egocentrism that merely cherishes itself in the other...
There are two parts to this. The clause before "that" means "obsessive desire is due to egocentrism".
The second clause uses "that" as a relative pronoun to represent "egocentrism". If you turned this clause into a sentence on its own, it would be:
Egocentrism merely cherishes itself in the other.
This sentence expresses a quite complex concept. To put it in overly simple terms, it means that the person loves themself (egocentrism), and what seems to be passion for the other person is really just a way of loving themself even more. They see their own ego reflected in the other person. Even more, the locus of this "cherishing" (a very strong word for "loving") is within the other person.
The preposition "in" is therefore the right word to use here. If necessary, it could be replaced by "within" to emphasise where the "cherishing" takes place.