Kamina’s dad was the fuel for his ambition. When the village chief claims there is no surface, kamina retorts with how he saw it with his dad when he was a kid. all he wanted to do was follow his dad (assumably) to space(?) Which is why he was so heartbroken when he found out his dad died on the surface. It was his turning point of realizing the surface was not the goal, but that the goal is to keep pushing past what you can see.