Zaibatsu Tears is set in the twenty first century, where the Earth is run by the corporations. The general populace work for and are expected to give their loyalty to the corporations first and foremost. Enforcing the corporations laws, are the saiyubogu, who in exchange for their cybernetic parts, indenture themselves with the hope of eventually buying their freedom.
The story stars Pi, a saiyubogu who is indentured to the Domaiyoshi Corporation. She needs only one big case to pay off her debt and buy her freedom. The opportunity drops into her lap when a high ranking executive is murdered and she is given the task of tracking down the killer. During her investigation, she discovers that the killer is the only man she had ever loved.