SoltyRei (2005)

Roy Revant is a bounty hunter working in a town that is covered by an aurora-styled force field after it underwent a radiation disaster known as the Blast Fall. Roy lost his family in the Fall, his wife died from radiation and his daughter Rose went missing; now all he lives for is to find and reunite with his daughter. Into Roy's bleak, overcast life enters a ray of sunshine: a young girl with no memory and a big heart. Roy reluctantly takes in the girl, who he names Solty, and the two set out on various missions across the City. However, as time passes, they begin to discover secrets about the town, deeply linked to Solty's past and to Rose, now a revolutionary-outlaw; even more surprising, Roy begins to open his heart to a devoted Solty, who considers Roy to be her father. What will eventually become of Roy and Solty?