Second season of Da Wang Bu Gaoxing.

As the Holy Empire rises to power, the neighboring lands begin to gradually fall under its control. The Empire's conquest eventually reaches the small island of Erin, home to the Gael tribe. There, a priestess named Riannon is kidnapped to be offered as a living sacrifice to the demon king Arawn, a malevolent being rumored to have caused untold destruction in the past. Riannon's brother, First Warrior Arthur, rescues her, when Arawn suddenly materializes before them as a handsome grey-haired man. Hiding his true identity and remaining enigmatic, Arawn pledges his power and leadership to the tribe's cause and joins Arthur, Riannon, and their merry band of friends—including a talented swordsman, an agile hunter, and a group of ecstatic pixies—as they fight back against the Empire, while uncovering the dark secrets of the land along the way. [Written by MAL Rewrite]

UFO Princess Warukyure, aka UFO Princess Walkyrie is about a princess from outer space who accidentally crashes on earth, where Kazuto desperately tries to maintain the public bath of his grandfather. Due to circumstances, Kazuto receives part of princess Walkyrie's soul which forces her to stay there with him. But that's not the only problem ... because her soul lost strength, the princess transforms both mentally and physically into a little kid! (Source: AniDB)

The third season doesn`t have a particular story behind everything (like "Valkyrie Ghost" in the second season). It just tells 6 stories about the life of Kazuto & Co. with some additions: Raine and Chorus get a house on earth, the last three Valhalla princesses each get an episode, and in the last episode Kazuto and Valkyrie, who in the same episode managed to stay adult, >try< to marry again. (Source: ANN)