Eun-jin was separated from her older sister Yu-jin when they were kids at an orphanage. While growing up, Eun-jin became a gangster and adopted the nickname "Mantis." Upon discovering that Yu-jin had cancer, Eun-jin demanded that the doctors perform an operation; however, they refused. The dying Yu-jin wished that her sister would marry soon, so Eun-jin went on a blind date under the advice of her underling Romeo, who invited a stylist to design the appropriate makeup for Eun-jin. However, the date was a disaster and Romeo was sent to find someone else more suitable.

Later, while Eun-jin was smashing up a car in retaliation against two men, a man ran up to protect her, but was accidentally hit in the head by Eun-jin. The man, Kang Soo-il, was a simple but kind-hearted man. He seemed perfect for Eun-jin and he later married her. Yu-jin spoke to Eun-jin about her desire to have children and Eun-jin set out to get pregnant. She forced her husband into several occasions of sexual intercourse.

While Eun-jin was out for a meal with her group, she was approached by a man from a rival gang, the White Sharks. She stabbed him in the head, barely missing his eyes. Afterwards, there was a meeting between Eun-jin and the White Sharks and a showdown was arranged between Eun-jin and Nanman.

Eun-jin and Nanman fought fiercely. It seemed that Nanman had the upper hand after stabbing Eun-jin in the stomach. However, as he went to finish her off, she moved out the way and Nanman fell down a cliff. However, Nanman managed to climb back up and tries to strangle Eun-jin. Eun-jin found a way to escape and stomps on Nanman's groin.

Soo-il eventually found out that Eun-jin was in fact a gangster, and wanted her to give it up. Eun-jin discovered she was pregnant and told Yu-jin. Later, Yu-jin then died of cancer in front of Eun-jin after telling Eun-jin that her baby needs a father.

Later, Romeo died in the arms of Sherry, after being stabbed by five street punks. His friend Andy mistakenly believed it was Nanman and the White sharks who killed Romeo and set out to take revenge on them. Upon arriving at the White Sharks' warehouse, Andy and the rest of his group discovered that they were heavily outnumbered. The pregnant Eun-jin went out to fight the gangsters, but suffered a miscarriage after suffering a vicious attack by Nanman. Eun-jin told Nanman to stop kicking her in the belly as she was pregnant. Nanman then revealed that he had become a eunuch after his earlier showdown with Eun-jin.

As Nanman was about to stab Eun-jin, her boss turns up and pleads to the White Shark to spare her life in exchange for some documents. Soo-il found out that Eun-jin was pregnant when she was in the hospital. He takes revenge on Nanman by dowsing him with kerosene. As he was about to light it, Soo-il was restrained but the Nanman foolishly ignites himself, along with 64 other men, when attempting to light a cigarette. The film ends with Soo-il as the leader alongside Eun-jin, who is starting a showdown with another gang leader.