The strange and magical events of the last season have left Kazuto with two Valkyries. He now finds himself living with and looking after both a teenaged-princess Valkyrie, as well as the child-princess Valkyrie! And they still have not yet gotten married... (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)

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 deadly confrontation with the Devil King, Oda Nobunaga is over, but the struggle for supremacy continues in Warring Countries-era Japan, as the armies of Takeda Shingen and Uesugi Kenshin repeatedly engage battle at Kawanakajima. Meanwhile, on the easternmost side of the battlefield, two outstanding characters bound by destiny—one clad in azure and the other in crimson—are about to clash in a long-awaited, decisive duel. Then a sudden dispatch informs that a huge army has surrounded the forces of Takeda, Uesugi and Date at Kakanakajima. Their leader is Toyotomi Hideyoshi, the man who inherited Nobunaga's dreams and ambitions, and who is now going to bring havoc over Japan once again! (Source: Production I.G)