Sun-ken Rock is a Manga/Manhwa/Manhua in english language, Seinen series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Ken is a Japanese man, and Ken’s love interest Yumin moves to Korea to become a police officer. He then decides to follow her to also become a police officer but instead ends up becoming the leader of a small Korean gang. What will happend to Ken?