Cheonssisegaui Mangnaniga Doeeotda

There was a nameless warrior who devoted his life to guarding and serving Cheon Mu-ryang, the eldest young master of the Cheon Clan. In the end, he was betrayed by Cheon Mu-ryang and met his death. But when he opened his eyes again, he found himself reborn as the very man who killed him: Cheon Mu-ry