Vincenzo Casano (Song Joong Ki) grew up in Italy and became a cold-blooded strategist and lawyer for the Mafia. He looks like a nice person, but he can take revenge without hesitation. He also has excellent negotiation skills. Vincenzo returns to South Korea after the outbreak of war in mafia circles.
He falls in love with Hong Cha Young (Jung Yeo Bin), an elite lawyer who works for the large Usan law firm. She is one of those lawyers who are willing to do anything to win a case.
Jang Joon Woo (Ok Taek Young) is a law intern who works for Usan alongside Hong Cha Yeon. He grew up abroad and has good looks and an innocent smile. He trusts and admires Hong Cha Young.