The B Story
Now that your hero is in their topsy-turvy world, the B story plot begins. Yep, a brand new plot.
The B story/problem is usually introduced by a new character. This new character is a reflection or a version of your hero, having some of the same flaws but to a more detrimental degree. This way your hero understands how the world views them, and that they need to change. They introduce a new set of problems and their failed ways of dealing with them, so your hero can find the best way to solve the problem. By dealing with their issues, your hero learns who they truly are and what they are capable of. They achieve enlightenment.
Another way to create a B plot, it to have the new world influence your hero into changing. By changing the setting, you can create new problems your hero must solve, and by solving them, they grow as a person.
So, let’s say your hero starts lives in a lush glade with beautiful waterfalls that spill out into crystal clear pools. One day they are sitting in their favorite, secret cave behind a waterfall, relaxing peacefully, maybe dosing off, and BOOM an asteroid hits the Earth near the glade. Everything is on fire, the water has evaporated from the intense heat, and everyone they know is dead. (I know it’s harsh, but we have to hurt our characters for them to wake up and become what they need to become.)
This new dry, hot world you created is the B character. It is what pushes your hero to pick up the pieces, or leave the pieces, and learn to do things on their own and in a different way. Maybe they were considered a slacker by their family, but now because of the change to their environment, they are forced to change their ways, survive on their own, and grow up.