He was a hero. Your hero. Your older brother Rivus was everything you wanted to be. It was hard after he left to the army. It was harder after he died.
He wouldn't have wanted you to mope in your room forever though. On the long journey to heal and grieve, you've decided to celebrate your memories with him by making paper air planes to explore locations you've spent the most time with him. The house you grew up, the lake where you went camping, the forest where he died...
With Zel, the robot he built for you, to help upgrade your planes, you should be able to go further and farther than ever. Whatever it takes to go the distance and lay your laments to rest.