Soo-Jin has been imprisoned for killing her husband. Her motivations are not given, but she says "he was a bad man".
In Cheongju Prison, Prisoner 818 takes advantage of her fast work in sewing duty.
On Sun's first day of sewing, Soo-Jin volunteers to train her, and the two become friends. Sun is shocked to see Prisoner 818 take Soo-Jin's work to get outside privilege, which Soo-Jin sadly confirms to happen often.
Sun bemoans to be giving extra work to Soo-Jin, but Soo-Jin replies she enjoys teaching her, as it helps time go faster, and as she rarely goes outside anyhow. As Soo-Jin hints at liking to paint, Sun decides to stand up to 818, allowing Soo-Jin to go outside.
When Sun finishes her own work, she meets Soo-Jin outside. She had painted her three sisters, whom she missed, at the mural, and invites Sun to paint along.
She makes a cameo in this episode, sitting in the cell, sewing a blue cloth (possibly Sun's uniform, which had been cut by 818) while Sun reads a book beside her. Until a guard comes to inform Sun has a visitor.