Each week, Kanata, a reserved and innocent exchange student, faces the persistent romantic pursuits of Alex, a young mafia leader who continuously invites him for coffee. Despite showing a hint of response to Alex's direct yet cheesy gestures, Kanata conceals a critical secret — he is the feared assassin known as 'Black Swan,' hired by a rival clan to eliminate Alex. Operating undercover, Kanata patiently waits for the opportune moment to carry out his mission. However, Alex remains vigilant and refuses to lower his defenses, compelling Kanata to take a risky step by making himself a target in an unexpected twist of events!