Take me Where the Sun Sets

It's a divided and harsh world. The human race has split in half- into two races. The Treewalkers in the sky, running across the treetops, and the Ground-dwellers, sprinting through the grass and jumping over ditches.

In the Place of Black Stars, the Forbidden Land, there is no such thing as peace. Tensions are high and you're not even safe in your own home. Each race lives in fear of the other, which leads to violence.

Get up on time. Show your face at least twice during the daytime. Get inside before sundown. Don't get left behind. Don't touch the ground unless you have a valid reason. Trevor Calton is used to all of the rules in the Black-star Treewalker's world. He's lived here almost his entire life, and he's always been a risk-taker. He and his friends constantly dare each other to do things like race across the giant clearing, scare the Ground-dwellers, and get back to their homes right as the last sliver of the sun sinks below the horizon.
However, one day, they crossed the Ground-dweller's well clearing to taunt the short-legged race. Long story short, Trevor fell due to an arrow wound and was thrown in prison the next morning. There, he meets friends who are gone in an instant, leaving him to walk through the cold, damp, underground corridors alone.
That is, until he met her. Larxene Diene. She helped him get back up and running, and became his friend. For the remaining two years he was there, she helped him out. They became more than friends. It seems like life is back to normal as they run free on the surface- until Larxene is brought back down, and disappears when she learns of Trevor's whereabouts and status.
Trevor has to hide his identity and keep secrets, locked away in journals. After all, no one will know who you are if you use a different name, different identity...

..right?