Although there’s a lot to think about in regards to Yukiko, I think the MC is just as interesting... there are more than a few strange things that seem to have happened specifically to him, not to mention the current strange things going on around him, so I feel like him and Yukiko are pretty even main characters imo. I think they both have great potential as characters, if the author does a good job developing them along with the story it’ll be fantastic, but if he doesn’t for either one of them I think it’ll really fall apart.