I knew the name Balsa seemed familiar! This is from the anime!!! Which was awesome and expands more than the manga has. Balsa is a famous spear warrior that comes upon a mission to keep a prince safe. But the danger goes beyond just from those from the palace but the spirit world has now become involved. Super interesting. Action, fantasy, awesome strong female lead, and I forget his name but that childhood friend dude, I ship them! Watch the anime, read the manga, both are awesome. May seem slow at parts, but what story doesn't have its draggy moments.
Seirei No Moribito