She is Dong-young 's closest friend since childhood. At the end of the series she is shown to be engaged to the Blue Dragon, Woo-Hyun watching Dong-young and Bi-wal happily.
When Ah-Hin was born, her father, the former White-Tiger, had a lover already, giving birth to her. But the King made an arranged marriage, taking him the former Red Phoenix (a woman). This Red Phoenix gave birth to Ah-Hin's half brother . The Red Phoenix left and took When Ah-Hin was a young child, she was considered a boy often since she was such a tomboy then. The former White-Tiger drilled her everyday, unable for Ah-Hin to dress up as a normal girl. As the time of that era, the Blue Dragon was snapped from the former Blue Dragon, commenting that Ah-Hin was ahead of sword training and is skilled in martial arts. Woo-Hyun , wanting Ah-Hin to quit working at becoming her destiny, he kept bullying her everyday.
Despite so, he had a crush on White-Tiger, but mistaking her as a boy. Ah-Hin cried, then the Tree-Spirit came by to comfort her, telling that he will become her friend. That made her happy. But before so, she saw an apple tree. She thought the Black Turtle and the Blue Dragon will become more friendly to her. But she overheard them taking about her, commenting how ugly and dirty she is. She became sad and angry, stating that she is promising to never show up in their faces ever again.
Ah-hin is considered to be "one of heaven's greatest beauties". She has pink coloured eyes and hair and is described by Mi-hyang as "Petite, Big eyes". Her hair changes somewhat throughout the series. At the beginning she generally wears it out, with a thin fringe in front, it is very long (almost down to the floor in the first few chapters but it gets shorter, ending up just a bit past her waist) and curls at the bottom.
Towards the middle of the series Ah-hin begins to wear her hair in different ways, it generally becomes shorter, somewhat wavier/curlier and the fringe becomes a thin fringe underneath a pronounces split/part in the front (in short a more pronouced fringe) although this is probably just due to the fact that the style that the artists drew hair in changed somewhat throughout the series.
When she was younger Ah-hin was often mistaken as a boy due to being unkempt and 'dirty' from her fathers harsh training. In a side story, it is explained how she became as pretty as she was today (due to Dong-young).
When she was young, due to looking like a boy and being bullied and treated harshly (by her father, Woo-hyun and because people often spoke about her behind her back due to her mother) Ah-hin was very shy and timid. However, after Dong-young's "Kim Ah-hin Lady Making Project" she discovered her "power" (her beauty) when she stopped some kidnappers just by looking at them and then again when she gets her father to allow her to dress up using her smile, she becomes the Ah-hin that is portrayed in the Manhwa today, a pretty, strong girl who likes to (and "always does") get her way (using her beauty). Ah-hin mentions to Bi-Wal that being an illicit love child, she has developed an ability to see people's true intentions. Although Ah-hin is described by Ee-jung to only solve her problems via brute force (same of Dong Young), this is shown to be untrue as she constantly manipulates people to get her own way (after learning how to harness her beauty as her power) such as when she tells Woo-Hyun to let Dong-Young stay on earth in exchange for a date, rather than fighting him head on.
Ah-hin has been Dong-Young's best friend since childhood. They met when they began sharing a sword-fighting teacher together when Ah-hin was training to be the White tiger and Dong-young (who was supposed to be raised as a boy) was training to be the Winter General. Ah-hin always protects Dong-young when she gets into trouble on Earth (as her powers are sealed).
Ah-hin is Ee-jung's older sister and has her brother wrapped around her little finger. However, she does love her brother and encourages him to smile and have fun more. Often stating "Stop frowning! You're ruining your pretty face!".
After finding out he is the Blue Dragon Ah-hin initially hates him for bullying her when they were little, however, she 'saves' Dong Young by agreeing to date him and continues to do so, as she has actually had feelings for him since she was little. In the end the two get married after the Blue Dragon's family propose Woo-hyun marry Ah-hin (and Ah-hin's father accepts 'just because it's the Blue Dragon' as stated by Ah-young).
Ah-hin is the only one of the four guardians who realises (at first) the way that Doh-hyun feels about Dong-young (because Dong young and Woo-hyun are oblivious, Doh-hyun is in denial and Ee-jung just doesn't care about what happens unless it happens to his sister). She acknowledges this but doesn't really do anything about it.
Ah-hin and Mi-hyang's relationship can be described as somewhat strained. When they first meet, Mi-hyang mistakes Ah-hin for the princess (and thinks nothing of Dong Young) and is extremely jealous and mad at her because she sees Ah-hin talking to Bi-wal. She even goes to the point of confronting her and calling her "U-G-L-Y" which causes Ah-hin to get mad at Mi-hyang as well (Ah-hin quote "Leggo! I'll kill that bi***), later, they almost end up fighting again after Mi-hyang heals Doh-hyun, at which Mi-hyang thinks to herself that even though Ah-hin "doesn't look like it" she's actaully a "devious bitch". At the end of the manwha, when watching Dong-young and Bi-wal, Ah-hin seems more tolerant of Mi-hyang, but finds her and Doh-hyuns incessant crying over their 'first loves' to be annoying.