Jinjuu Houretsuden

From Storm in Heaven: In ancient China there exists an alternate dimension called Jusenkai, whose inhabitants, the Senkaijin, possess tremendous powers. One of them, YanLang, fled to Earth along with his rebel army after being defeated during his attempt to overthrow the Emperor. In order to capture the fugitives, the Emperor sent his elite soldiers to Earth after them. LiFang has been traveling alone to find his father's murderer when he picks up a sick and injured man. That aloof man, TuoRen, turns out to be one of the imperial soldiers sent to earth to hunt and capture the Senkaijin rebels. While his comrades work in pairs, TuoRen prefers to be alone. That is, until the strangely powerful human, LiFang, decides to follow him on his quest. The volume 5 extra is the unrelated short story Time Lag.