Sun-ken Rock

Sun-Ken Rock (サンケンロック, 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
The story revolves around Ken (the main protagonist), he's a Japanese high school delinquent that was orphaned young due to his family's involvement with the Yakuza. The only thing that motivates him to take action is through his romantic affections for a classmate, Yumin (the daughter of the very Yakuza group that killed Ken's parents). After learning she decided to move to Korea to become a police officer, Ken left his life in Japan behind and tried to follow in Yumin's footsteps; due to unforeseen circumstances, he incidentally becomes the head of a local gang and tries to hide it from Yumin. As the leader, the gang is renamed the Sun-Ken Rock Group. At the first, the gang only consisted of few members and didn't even have a base. As the story progresses The Sun-Ken Rock gang becomes bigger as they recruited new members and take over other gangs' territories and investments. The Sun-Ken Rock Group acquires an MMORPG company, a large casino, one of the biggest television media companies in Korea, as well as garnering political favors (making them the most powerful gang in Korea). However, throughout all of this, Ken has done his best to evade revealing himself to Yumin as a gang leader as she despises gangs. Ironically, Yumin was groomed to become an advanced plant in Korea to help her Yakuza group lay the foundations to expand their hold into South Korea; due to Yumin's refusal to join the "family business," their plans were stalled as various members either tried to take her back to Japan or try to get her back into Yakuza control. In between Ken's rise, he and Yumin got closer and Yumin started to have feelings for Ken. However, things were always complicated by the interference of either Ken's gang activities and/or Yumin's Yakuza connections. The turning point in the story was when she was kidnapped by her own group and Ken was exposed as a gang leader in his attempts to rescue her from his greatest rival, Kim Ban Phong (a Vietnamese-Korean that has a vicious score to settle with Ken).

Official
http://sunkenrock.com/