Jacobo Tamura serves as the localized Spanish name for Kousuke Tamura. He is the brother of Yuusuke Tamura and uncle to protagonist Eriko Tamura. After Yuusuke dies in a car accident, Jacobo assumes control of the family's music company, Tamura Productions. His primary objective becomes systematically undermining and destroying Eriko's burgeoning singing career, actively opposing her path as an idol against her parents' original wishes.

Jacobo orchestrates schemes to sabotage Eriko's professional opportunities and public image. A significant manipulation involves Rei Asagiri, whom he promotes as a rival idol while fostering her resentment towards Eriko. He deceitfully suggests Rei is Yuusuke's abandoned daughter to exploit her insecurities and direct hostility towards Eriko, serving his agenda to damage Eriko's career through Rei's actions. It is later revealed Jacobo is actually Rei's biological father, making Rei and Eriko cousins.

His antagonism extends into personal attacks. Jacobo leverages his position to disinherit Eriko, stripping her of family wealth and company resources, forcing her to rely solely on her idol work for financial independence. He maintains his role as the central antagonist driving much of Eriko's professional and personal challenges throughout the series.