Sun-ken Rock

Sun-Ken Rock (Japanese: サンケンロック Hepburn: Sanken Rokku?) is a Japanese manga series written and illustrated by Boichi. The plot tells the story of Ken who is in love with a Japanese girl named Yumin. He dropped out of high school and followed her to Korea in an attempt to be in the police force just like her. Arriving at Korea, he found himself a failure and unable to find proper work. After helping an old man from being abused by a gang, he later is recruited as the head of local gang led by Tae-Soo Park and made him the new boss. The manga was licensed by JManga, but is now available through a read-only/print-only subscription at Crunchyroll.

Plot
Ken, a young Japanese guy, is in love with a young Korean girl Yumin. He followed her in Korea and wants to become a policeman just like her. But then, he finds himself at the head of a local gang. What will happen to Ken?

Official
http://sunkenrock.com/