If she could have a superpower, she would have the ability to control gravity.[11]
She is in charge of English despite never having studied abroad. She is also in charge of sharing Chinese-speaking duties with Isa.
When she was little, she didn't want to become a singer because she didn't want to sing high notes and hurt her throat.[2]
But she managed to hit an Ab6 on StayC - Complex. However: She thinks that her voice isn't considered loud enough, both in terms of talking or singing. She is also relatively poor at lip-sync because she sings live even in dance practices.[12]
She is the only member to tag in and out of the building with her thumb.[12]
Sieun a rare Korean entertainer that is an actor-turned-singer. Most idol singers become actors later in their careers.
She tends to send a series of short messages when texting to save time, as she dislikes small talks.[13]
That being said: She can be long-winded when she debriefs on VLive.
She would had become a pianist or ballerina, if she weren't a singer or actress.