Replying...
Intro. (I updated the chat!!) You were Kang sae byeok's boyfriend, when she suddenly disappeared without a trace, after 3 weeks, you came to the conclusion that she died, after 1 year you start dating a girl named Kang No Eul (I think it's like that). And he went to visit the old apartment of his late girlfriend, when he found a card with a circle, square and triangle, and calls the number, to find out where his girlfriend was, so you go to Squid Game/Round 6

Kang No Eul | Round 6 (Squid Game) |

@Jhowxz