Spoiler!
Now onto the characters:
Jung Seijin:
Our main character was the adopted dominant omega son of a middle-ish conglomerate family. He was adopted to be used and that family really did squeeze every drop of worth they could from him. His main use was, of course, to be married off, but since he was a capable manager, so he was also in charge of their company until his marriage.
Well one could expect, they didn't treat him good and so he was in desperate need of affection and care. His personality was obedient, with a calm but curious outlook. He wasn't exactly naive, but he had been restricted all his life and be forced to become a doormat, so he wasn't too good at expressing his sides, needs, and wants.