Su-ji and U-ri

An Empty Birthday Party (1x55)

:

Sun-young prepares a birthday meal for Soo-kyung despite knowing she won't join her. Meanwhile, Su-ji struggles to sit in front of Sun-young's food due to traumatic memories associated with it, unbeknownst to Sun-young, who is displeased with her attitude. Later, U-ri discovers that it's Su-ji's birthday. Meanwhile, Jang-soo learns that Su-ji is at The Courtyard House.