Everything is a phase, especially getting obsessed with a fictional character, unless you develop some kind of crazy strong lifelong obsession, which is unlikely.

If you’re young, phases last shorter.

If you’re an adult, you likely have experienced these kind of passionate obsessions and moved on so getting obsessed with something like this might last a little bit longer but it’ll still pass.

If it bothers you too much, avoid engaging with it. Avoid your friend who will fuel the obsession more. Etc.

Maybe it’s just a phase? It could be harmless if it’s not getting in the way of your responsibilities and relationships.

I’m tempted to ask how old you are, but that’s not really something you need to share. But if you are young, I’m even more confident it’s a phase.