Under The Gun.

Meet ‘Goh Gun’, the ‘It’ Boy of Sunhwa High School, who is admired by his friends for his charming looks and impressive skills in Texas-style poker game, Holdem. However, when his younger sister Jun-hee falls ill with an incurable disease, his life takes an unexpected turn. With their father losing all their savings in gambling, Goh Gun takes the responsibility of saving his sister at any cost.