'PM 10:01' is a 'Yoo Ji-min's text message' in White Day: A Labyrinth Named School (Remake).
It is exclusive to the PC/PS4 remake version.
You can see this message when you play the 'Yoo Ji-min' route.
It is found in the Messages Menu. (Mobile Phone - Gameplay element feature)
How are you, my little princess?
Forget what your father said last time.
Just take care.
I'll visit you soon.
우리 딸 잘 있지?
아빠가 한 말 신경 쓰지말고
몸 조심히 잘 지내렴
엄마가 곧 갈게