Please be aware that this is a promotional one-shot for the novel of the same name.
From MangaDex:
Scarlett has lost her partner six times to her friend, but always forgave her friend's pitiful yet beautiful words.
"It was for you, Scarlett. Haven't you always said that any man who can be taken away easily isn't yours?"
However, when the veil is lifted, Scarlett decides to seek revenge against her friend.
In front of her friend, Scarlett passionately kisses her friend's fiancé.
"I'm sorry I didn't see your ill intentions, but you shouldn't have underestimated me."
All of this is my retaliation.
Mysterious and unpredictable.