In Seung Yoon is Queen's younger brother and is the new heir to the YK Corporation after being born, considering his sister Queen was going to be previously. He is often seen requesting a chocolate parfait from his butler.
Despite his stature, In Seung Yoon feels the need to "approve" of who his older sister can date. It is implied that his is superior in everything except his weight.
In his spar with Jae Gu Song, Queen advises that Jae Gu Song shouldn't look down on him, assumably due to his stature.
- He enjoys video games and would rather be playing one instead of interacting in his duties as an heir to the family's business.
- He also enjoys watching the Pokemon series.
- We can assume that his favorite food is chocolate parfait since he is always seen ordering it.
- When he and In Gyi visited Jae Gu's house and Dal Dal was cooking for them, he would rather eat from his personal chef and not from an unlicensed cook.