白龍公爵ペンドラゴン

After 10 grueling years as a monster hunter in the Devil’s Army, Raven Balt was given his final mission: guard Allen Pendragon, heir of a formerly glorious dragon-taming family. But when Raven and Allen are both killed as part of a conspiracy, Raven wakes up seven years in the past inside Allen’s body. To solve the mystery behind his death, Raven must find the legendary White Dragon to restore the power of House Pendragon. But does this mere hunter have what it takes to become a dragon master? (Source: Tapas)