Four hundred years have passed since the battle at the Alber Garden between Ku and Lei, and the two are widely remembered as legendary heroes.
In such an era, Bing Lanxue was an elite killer of an organization in the world of martial arts and a rare holy war angel. During a mission, she met the summoned ancient hero king Gilgamesh and was rescued by Lei and Ku who arrived. Bing Lanxue learned that Lei and Ku had become the "pillars" of the world, and at the same time received the task given to her by the two...
So Bing Lanxue took Saber's soul and appeared in Konoha as Lei...