Sunset Soldier is the sixth stage in Sub-chapter 25, Scars of War.
1 Ursamajor will be spawned at the beginning of the battle, along with a wave of peons.
4 Ursamajor will be spawned with Squire Rel as the boss once you damage the base. However, a player can use the fact that they can be knocked back behind the enemy base advantageously. Ururun Cat, Bahamut Cat, Crazed Gross Cat, Macho Legs Cat, and both King and Crazed Dragon Cat are fantastic.
Still not hard, even in 4 stars. Just use ranged units that outrange Ursamajor and some meatshields. This stage is definitely the easiest one of this sub-chapter.