Taro Ootsuki operates as foreman of Squad E in Teiai Corporation's underground labor camp. He initially displays kindness and helpfulness toward inmates like Kaiji Ito, a deliberate facade to manipulate them into escalating debt. His core strategy involves enticing debtors to purchase food and alcohol he supplies, then lending them money to join rigged gambling games under his supervision.

Ootsuki orchestrates the Underground Chinchiro dice game, employing custom dice lacking numbers 1-2-3 to ensure his victories. After Kaiji exposes this cheating method with Squad C foreman Odagiri's aid, Ootsuki is pressured into a high-stakes rematch. Kaiji and other debtors deploy dice rigged exclusively for 1, exploiting Ootsuki's rule awarding 5x the bet for triple-1 rolls. This culminates in Ootsuki losing over 18 million perica and facing total defeat and humiliation.

In the spin-off *Chūkan Kanriroku Tonegawa*, Ootsuki unknowingly crosses paths with Yukio Tonegawa at a restaurant. Neither recognizes the other's Teiai position, allowing Ootsuki to interact without deference. They participate in an eating challenge, which both ultimately fail.

Ootsuki stars in his own spin-off manga *1-nishi Gaishutsuroku Hanchō*, detailing his daily exploits outside the labor camp. Key events include:
- Wearing a business suit at dive bars to mock salarymen while posing as an executive.
- Undergoing surveillance by Teiai blacksuit Miyamoto Hajime, who distrusts him.
- Instructing Miyamoto in relaxation techniques during work hours.
- Teaching subordinate Numakawa to enjoy leisure activities like festival visits.
- Attempting and failing to ally with fellow foreman Odagiri.

His enduring resentment toward Kaiji surfaces when he later watches Kaiji's "Bog" challenge via Teiai's surveillance feed, openly anticipating Kaiji's defeat. Additional background notes confirm his surname originated in live-action adaptations, and he maintains an interest in Japan's Bakumatsu historical period.