Fukushuu wa Futari no Hajimari

Am I An Adulterous woman?
What was the man's purpose in asking her to seek revenge on a lying man?

Kurusu Uta, who was afraid of men due to the abuse of her stepfather,
was dating her former senior, Ijuin Teruhisa, who had helped her, and they began dating. However,
one day, a handsome young man, Takahashi Rui, suddenly appears in front of Uta and tells her that Teruhisa is actually married. Rui, who
has vowed to take revenge on Teruhisa, asks her, "Would you like to join us in this revenge?"
Rui and Uta form a cooperative relationship and soon begin to have special feelings for each other, but

what will become of this relationship that began as a quest for revenge?