I'm (not) OK [SeulYong]

Characters

(For Taeyong, Seulgi and Johnny, the first/left pic is a younger version of them, and the second/right pic is nearly 30 years old them)

Kim Joon (Lee Taeyong):- First year high school student, best friends with Milly since they were three. His dad owns an huge tech company, so they're pretty wealthy. His mom died when he was two and his older sister never payed much attention to him and eventually moved to USA. He has a half-brother 10 years younger than him who he loves dearly, and they live together after his dad passed away and he took over the company, adding to it a hotel. He became one of the youngest, most successful business man in the country. Although very popular, he never had any interest in anything other than family and work.

Milly Hwang (Kang Seulgi):- A half Spanish half Korean girl, Milly was raised in Korea since she was two and met Joon a year later. She loves cooking and dreams of opening a restaurant when she grows up. She is always bubbly and ready to do anything fun and adventurous as long as Joon does it with her. She is always positive, even after her parents divorced and her dad returned to Spain, and never shows signs of pain or negativity.

Kim Jin (Lee Jeno):- Joon's 10 years younger half-brother, who is always happy to be with him. Jin is both the best student in school and the coolest guy. He is always up to date with all celebrity news and new trends, something Joon was never interested in. He knows what's right and wrong and decides to live with Joon instead of his mom after their dad's death because he loved his brother to death.

Milly's Mom (Shim Hye Jin):- After her divorce, Milly started seeing a different side of her mother. She became selfish, cold and used Milly as an excuse to get more out of people, saying her father left her and all, hiding the fact that Milly's dad still loved and supported his daughter and talked with her everyday.

Seo Youngho (Johnny Seo):- Youngho is an active student who likes to do anything possible to keep the three of them together all times, even though he knows that Milly and Joon go out without him sometimes. But he doesn't mind, because he loves shipping the two together, which always end up with him having bruises on his butt. He later becomes Joon's secretary since Joon wanted to have someone he could trust, and needed a good friend to be with him too. 

Kang Cheol (Lee Sangmin):- A rich brat in his 30s who owns a modelling agency.

Bae Noori:- The daughter of one of the high position employees in Joon's company, whose dad was close friends with his. She is kind of spoiled and wants to win over Joon. As if the task itself is not hard enough since Joon had no interest in dating or girls, Noori starts having a burning hatred towards Milly and tries to keep her separated from Joon as mush as possible.