10 years since the great war, tensions were mounting within the country of Wellber, which was barely capable of keeping peace, as war could commence at any time with its neighboring country, Sangatras. In order to avoid warfare, the king of Wellber, Haidel planned on marrying off his daughter, Princess Rita, to Sangatras` Prince Guernia. 
However, Rita stabbed her groom to be and ran away. Infuriated, Sangatras` King Ranbahnhof threatens to wage war unless Rita is captured and publicly executed within 14 days. In order to avoid the worst case scenario, Rita decides to head for the neutral country of Greedom. 
Meanwhile, the woman thief Tina sneaks into Castle Wellber, seeking its treasures, when she happens to witness the stabbing of Guernia by Rita. 
Whether it be by coincidence or necessity, Tina receives information that the "Wasp Man" she was after is in Greedom, her sworn enemy who took the life of her parents. 
Tina agrees to become Rita`s bodyguard as they head out to Greedom. Shouldering their fate and destiny, the two meet, leave, and set out on their journey. What awaits them is war or peace, vengeance or death... 
(Source: AniDB)

Wellber no Monogatari: Sisters of Wellber