The assassin Yurian is ordered to kill Duke Larkan of the enemy nation after marrying him. However, Larkan is an immortal being who turns into a lustful beast every night! After failing to assassinate him, Larkan makes a counteroffer to Yurian: He will find her missing brother if she tries to tame him. "If you want to kill me... try taming me first." A suffocating connection in the night. Larkan started the relationship to die, Yurian to kill him, but as time passes, they are instinctively drawn to each other...