Reborn as the Enemy Prince is a Manga/Manhwa/Manhua in english language, Adventure series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Imagine being kin to your sworn enemy. Killed in battle while defending his country, Bern wakes up in the body of the enemy prince, Kalian, and vows to avenge his people. But between taming an abusive half-brother and surviving his mother’s deadly web of intrigue, sweet revenge seems to slip further beyond his grasp at every turn.