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...