Amina

One of the heroines of the work, and the protagonist in "Cold Girl." A foreign girl kept by Kei. She was smuggled into the underworld through human trafficking, lacking both a family register and nationality, and was taught by Kei to be cautious of immigration authorities. Later, she gained freedom with a forged visa from Seki, a jack-of-all-trades in the underworld, allowing her to go out. Raised in an environment where murder and plunder were rampant, and influenced by her experiences in human trafficking transactions, she has a very severe view of "living" despite her young age. Therefore, she holds the belief that "life is more important than money."

She was once kept at a human trafficking ranch run by Nanbu (mentioned later) and was later bought by Seki. As a product of Seki's organization, she was kept by Macchan (mentioned later) and subjected to daily violence. Unlike the other girls, who had given up and showed no signs of escaping even when the surveillance was lax, she was the only one who never lost hope and was always looking for a good owner. Her eyes were filled with hope from the first time she met Kei. During the match between Kei and Macchan, she gave Kei a hint about the Tagalog passphrase, knowing she would be beaten by Macchan, and created an opportunity for Kei's victory.

Kei, who had won a total of 2.4 million yen by the time he defeated Macchan, took her in instead of the 2.4 million yen. Seki said, "I wasn't planning to sell her for less than 3 million," but (due to some trouble during the match with Macchan) he handed over Amina as a special case. According to Seki, "Her previous owner was also Japanese, and she received some education for about a year," so she can speak Japanese at a native level, albeit mixed with English and in broken phrases (however, she doesn't understand terms like "realism" or "first army," and there are scenes in the early part of the story where Kei teaches her Japanese). She sometimes plays mahjong with Kei, but there are also scenes where she plays other games (such as game software that allows her to experience "ski jumping").

In reality, she suffers from nephroblastoma, and because she kept it hidden, fearing "Kei would abandon her if he found out," it progressed to the terminal stage, requiring a kidney transplant to save her life, leading to her hospitalization (before Kei found out, she secretly received medicine from Seki to suppress the pain). Finding a donor for her kidney is almost impossible, but Kei aims to win the Ryuuou Championship to obtain the "list" that would make it possible.

In the "Sacrificial Pillar Arc," she is kidnapped by Hatori but successfully undergoes a kidney transplant abroad, cures her illness, and returns to Japan. Although she reunites with Kei, she cannot bear to see Kei suffer for her sake and begins to avoid him. However, she later participates in survival mahjong to protect Kei.

In the "Minagoroshi Arc," she becomes a hostage and loses half of her toes, but no aftereffects are seen. Additionally, the epilogue reveals that she and Kei became siblings through adoption, officially becoming "Amina Sakakibara" in the family register.

In "Cold Girl," she becomes a high school student and is promoted to the protagonist. She further hones her original courage. In the original work, she has dark skin, but in the movie version, it was changed to fair skin.