Female detective ERI has a tragic past—her parents were murdered by the ruler of the underworld. To avenge them, she enters a clandestine fighting tournament, concealing her identity while attempting to apprehend the crime boss. The ruler is a mysterious figure who only reveals himself to the tournament champion. As ERI advances through the matches, she faces one powerful fighter after another, enduring brutal fouls and intense psychological pressure. Despite her strong will driving her forward, she is nearly destroyed by last year's champion, a massive heavyweight wrestler. During the match, her identity is nearly exposed, leading to interrogation. Beaten unconscious with a shinai while wearing only a leotard, she is doused with water and interrogated again. Intrigued by her mental fortitude, the underworld boss allows her to compete once more—this time in a grueling 3-on-1 match. Amidst the battle, she suffers harsh treatment including forced submission, creampie, and extreme interrogation, yet the determined detective fights on, striving to seize her final chance at victory. [HAPPY END]