And why does sun set cannot be bring over to newgame?
Because is overpowered. It increases the Heros stats by a bit and also increases his Sun Damage. Not to mention the armor. It would almost nulify the damage dealt to him in the begining of the game I think
you can find really low defense/cheap gear that boosts Sun and Fire affinity. the Poncho (it's a head gear) or something in Lordlake, and i believe there is a body armor somewhere that does the same.
Sun Ring is part of the sun set. i'm not sure if it was the poncho necessarily. just go to Lordlake, and you can find 1 or 2 things that boost Sun/Fire affinity.