It's Day 4. There is only one route, you just choose who to spend time with sometimes. Each wolfboi is getting a hangout with Fynn before the first choice. You'll just get different perspectives from each boi when those options come up, and Fynn will learn mildly different things about the world of Jotunheim/teach each wolfboi different things about Midgard, then it goes back to the single story route.
You could spend the whole game choosing a single wolfboi if that makes it easier for you, or choose a different one each time a point arrives where a choice is made. In either event, the story will still return to the single narrative route it turned away from. But this being Day 4, it's before all of that.
Hope that helps!