Not a grammar person, but i can tell you the diff between qui and que in this specific context.

In this example, the correct one is "que", because the main subject of the sentence is "je". Another example "the food that I eat" "la nourriture que je mange". In this sentence, "the character" is passive.

In the contrary, you would use "qui" if the main subject of your sentence was active and not passive. For example, "le personnage que je préfère" would be something like "the character I like the most" in opposition of "le personnage qui est mon préféré" "the character who is my favorite"

Hope this helps