Smile (manhwa) is a Manga/Manhwa/Manhua in english language, Action 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

Young-woo is on the verge of leaving his company after completing his final mission to eliminate a drug dealer.

Just as he is about to board a smuggling ship to China, he hears the news of his mother's death, who he lost contact with 20 years ago. There, he discovers he has a half-sister with the same name, Young-woo!

Meanwhile, the organization, realizing Young-woo is still alive, tries to eliminate him and find his sister..