Supernatural: My Start Shocked the Passing System

A modern cow horse traveled to a parallel world and was reborn as a person who fell to death during an outing. When he spent the night in the mountains, he encountered a strange marriage. The Shadow Groom was beaten to death by his companions, and the Shadow Bride was about to kill them. When his life was hanging by a thread, he did something that went against his ancestors for eighteen generations - he wanted to replace the Shadow Groom and marry the Shadow Bride.