- She has a younger sister.[1]
- She was revealed as the group's fifth member on October 13, 2020.[2]
- Her role model is Jessi.[3]
- Hobbies: Dealing with STAYC, visiting the group's fancafe, and drawing.[4]
- Specialties: Eating a lot, eating well, and drawing.[4]
- J has a pet cat named Tan.[5]
- She also has an old dog called Kkami at her grandpa's house.[6]
- She has two moles on the left side of her face: One above and one below the cheekbone. They are often concealed.[6]
- She loves Disney movies.[7]
- Dream Collaboration: Billie Eilish.[7]
- If she could have a superpower, she would chose teleporation.[8]
- Her favorite Disney princess is Rapunzel. As a child, she would tie curtains to her hair to imitate Rapunzel's.[8]
- She wants to take care of cats and dogs for her staycation.[9]
- She has many soft toys with bunnies and bears.
- According to Yoon, J is the Master Planker in the group.
- Because Yoon and J look alike, and J entered the company after Yoon, J was requested by the bosses to cut her hair.
- She really dislikes mint chocolate.
- She is not allowed to combine her last name with her stage name as "Jang J", as it has sexual innuendo.
- She would wake up from her sleep if she is hungry.
- She has the biggest hands and feet in the group, and have the longest fingers.
- She is very forgetful in terms of packing away her belongings, and tracking deliveries.
- She can hulahoop while walking.
- She trained with Sieun in JYP Entertainment, and they trained with Bae and Jinni of NMIXX.
References[]