It Was Love At First Sight, Mr. Villain!

Duke Adler, referred to as the greatest man of the Asgard Empire, is as handsome as a sculpture. However, he is also a serial killer, playing the role of the villain in a novel. On top of that, Princess Charlotte, who was politically married to him, was fated to be murdered on their first night together.
The predicament is that I am the princess fated to die at his hands on that night.
"It's a political marriage, and it's not as if we want to see each other anyway, so let's just meet on our wedding day."
It was evident that the villain was displeased with the idea of marrying me. Hence, I made a decision.
"It was love at first sight. So, please go out with me!"
With only six months left until the wedding, I resolved to carry out an undercover investigation by pretending to date him. People wouldn't believe my words, so I had no choice but to gather evidence myself.
Even though she had planned to reveal the fact that he was a serial killer by hovering around him...
***
"You said you fell in love with me at first sight, so what were you doing here with another man?"
A cold voice flowed into my ears.
"W-What do you mean? I was just dancing to ensure there were no disruptions at the banquet..."
The nape of my neck heated up from the hot breath brushing against the outer edges of my ear. The contrast between his warm touches and the cool tone of his voice intoxicated me even more.
"You called his name so affectionately, as he held you tightly in his arms."
"Gasp."
Unable to escape the strong scent that clouded my senses, I held my breath. My whole body tingled from the strange sensation spreading from my neck to the rest of my body. He tilted his head and said...
"If there's someone else's scent coming from you... I'll have an urge to kill."