Three siblings who care for each other in the wake of illness and death. 

Jung Siblings:

- their mom died when Soojung was 5 

- because their mom is gone and dad (Yunho) works a lot to care for the family, Yonghwa has taken it upon himself to care even more for his younger sisters

- Yonghwa and Sooyeon are especially close due to their close ages and their love of music

 Yonghwa

- 18 years old

- older brother of Sooyeon and Soojung

- passionate about his music and equally passionate about being an overprotective older brother

- best friends with Jonghyun, Minhyuk, Jungshin

Sooyeon (Jessica)

- 17 years old

- middle child

- as a child, got sick very easily so she didn't make many friends and was painfully shy around new people so her parents let her be home-schooled

- a talented pianist

- best friends with Seo Joo Hyun

    - started piano classes with Joo Hyun's mom

Soojung (Krystal)

- 12 years old

- little Jung

- looks up to her older brother and sister

- wants to be a doctor to help her sister

Seo Joo Hyun (Seo Hyun)

- 17 years old

- younger sister of Seo JiSeok

- called Seo Hyun/Hyunnie by Sooyeon; called Joo Hyun by her family and others

- studies in the same high school as Yonghwa though one grade lower