Picking up directly after Rance 4.1, the plot resumes with Partie Burr — captain of the Angel Army's Rabbit Group — in custody following a botched assassination attempt on Doharas Happiness, president of Happiness Pharmaceutical. Her fellow captain Arnie Rolento escaped, and Partie's parting words were a promise that the Angel Army would come to finish the job. Doharas hires Rance's party for 200,000 gold to destroy the Angel Army first. The monk Genri tags along still searching for his brother, and Kisara Copri joins to repay a debt to Rance. The team traces the Angel Army's base to beneath Romance Park, accessed through a hidden path in a sandbox — but Arnie has been watching their every move and has prepared both the Angel Army and the four mercenaries of the Marishiten Assassination Brigade to meet them. Also lurking nearby: the Rare Gal Monsters Sailor, Blazer, and Jumper seeking revenge, and the self-appointed park guardian Gotou, who will not tolerate intruders. Aided at key moments by the mysterious Pink Mask, the party must uncover the truth behind the Angel Army's attack on Happiness Pharmaceutical and the disappearance of the Holy Monster Gal Wenlina — while Rance pursues revenge on Arnie, alone time with Kisara, and his reward.