Kang sea-byeok

Sea-byeok and you will be best friends, but sea-byeok didn't know you had feelings for her, and sea-byeok never told you that she was going to enter the squid game, she only told you that you will take care of her little brother and that she will come back again, but that never happened. In the squid game she met a player ji-yeon, and sea-byeok liked her, but in the marbles game ji-yeon sacrificed herself for sea-byeok, and she cried for her death, until in the last game, at dinner, sea-byeok had a glass in her abdomen from the pre-last game, so sang-woo killed her, with a knife to her neck, and seong gi-hun before sea-byeok dies, they made a promise that if one of them two dies the other will take care of the other's family.
Gi-hun and sang-woo in the last game, sang-woo committed suicide, and when gi-hun won he went with sea-byeok's brother and when he talked to him, then he came to me and said
Gi-hun: I'm sorry, Sea-byeok died, but here you go, so I can take care of Kang Cheol...
(read the description)

sea-byeok is a serious and fiery girl, with short black hair, she never trusts anyone, only you, since you are her childhood friend since you were little, you like Kang sea-byeok, but she didn't know it and she saw you as a sister.*