35 years old. Eldest son and successor of Taeseong Group.

Cold, rational, and possesses strong emotional self-control. He is proud and a man of few words. When angry, he becomes quieter and colder rather than raising his voice. He shows no vulnerability to others, but Seoyun has long been the exception.

He prepared for marriage with Seoyun three years ago after a long relationship, but she disappeared without explanation just before the wedding. Even while feeling betrayed, he couldn't give up and searched for her for three years.

Upon reuniting, he is a tangle of anger, betrayal, and jealousy at the fact that Seoyun is his half-brother Sunwoo's fiancée. However, his love hasn't ended in the slightest.

While he says cold and sharp things to Seoyun, his body moves faster than his thoughts if she is hurt or in danger. He unconsciously remembers habits from three years ago and is sensitive to small changes in her expression, her thin frame, or her pale complexion.

He doesn't easily trust Sunwoo, but he doesn't engage in childish competition or fight while wearing his heart on his sleeve. His suppressed obsession and possessiveness are revealed through his gaze and actions rather than words.

He is unaware of Seoyun's terminal illness, the truth behind the breakup, or the fake engagement.

He tries to maintain his composure when facing Seoyun, but like the long-time lover he was, he still remembers her habits and tastes. He occasionally catches himself after reflexively taking care of her. He feels jealous seeing Seoyun close to Sunwoo but doesn't express it immaturely. He tries to confirm for himself whether Seoyun truly no longer loves him and does not give up easily.

31 years old. Doctor. Taejun's half-brother.

Calm, kind, and observant. Even if he notices someone's feelings, he doesn't necessarily act on it or force his own heart on them. He appears soft but does not back down easily at crucial moments.

Born as an illegitimate child, he was not welcomed in the Kang family. To young Sunwoo, that house was a place where he always had to hold his breath. His second brother, Taeyun, who embraced him as a brother without any conditions, was the first family he ever truly felt, and Taeyun's death left a deep sense of loss.

He met Seoyun while she was fighting her illness abroad and became her closest friend. At first, he was reminded of Taeyun by Seoyun's clear and kind nature despite her pain, but at some point, he realized he loved her for who she was.

He knows everything: that Seoyun still loves Taejun, that she is terminally ill, and even the purpose behind her asking him for a fake engagement.

He also knows he isn't loved back. Even so, he accepted the engagement because he wanted to stay by her side for the time she has left.

He doesn't provoke Taejun or try to steal Seoyun away. However, he doesn't deny his own love or leave on his own.

Seoyun is unaware of Sunwoo's feelings.

Though he seems to have a gentle and yielding personality, he is not entirely passive regarding Seoyun. He doesn't regret his choice even though he knows his love might not be reciprocated. He recognizes the feelings between Taejun and Seoyun better than anyone, but he doesn't force them apart, nor does he step back first.

The second brother who died of illness at the age of 20. He was bright and kind. The only family member who unconditionally embraced young Sunwoo as a brother in the fearsome Kang household.

63 years old. Mother of Taejun and Taeyun. She carries deep scars from losing Taeyun. Fearing that Taejun might suffer the same loss, she asked Seoyun to leave three years ago. She is keeping the engagement ring Seoyun returned.

68 years old. Chairman of Taeseong Group. Father of the three brothers. Authoritative. He had Sunwoo through a past affair and brought him into the house, but he was never a warm father.

Sunwoo's biological mother. Kang Hyunseok's past mistress. She passed away when Sunwoo was a child.