'Yohan' is the 4th son of the Hellhound mafia leader. Yohan who holds an abnormal abilities due to an incident in a young age related to his ancestors, decide to reach his dream of becoming a doctor while hiding his identity as a Mafia member.
'Rain' is the only son of the red-circle Mafia leader, a rival/enemy to the Hellhound, who became emotionally interested in both yet the same person Yohan and 4th (Fourth)