Watanabe holds a senior executive position at Shijima Motors under Chairman Isshin Shijima's authority. He engineers the arrest of Momotarō Morikawa using false corporate espionage charges, accusing Morikawa of stealing proprietary self-driving technology developed by the chairman's deceased daughter, Ikumi. His relentless pursuit of a tablet containing this technology culminates in personally supervising a break-in at the Morikawa residence to secure it.

Within Heartland's dream realm, he embodies Bewan, chief adviser to the king. This counterpart mirrors Watanabe's ambition and duplicity, scheming to overthrow the monarchy by deliberately allowing the kingdom's giant robots to fail against the Colossus invasion. Bewan intends to seize power afterward by positioning himself as a savior with his own giant robot. His Heartland actions include imprisoning Princess Ancien and actively undermining the kingdom's defensive efforts.

Driving both personas is a desire to control cutting-edge technology for corporate and political dominance. Watanabe specifically aims to leverage Ikumi's software for a high-profile demonstration at the 2020 Tokyo Olympics, seeking to elevate Shijima Motors' standing and his own corporate influence. He operates without the chairman's explicit knowledge, manipulating his executive authority to advance these goals.

During the climax, Watanabe/Bewan escalates to direct sabotage. In Heartland, he emits a disabling "curse" from his cell phone during the Colossus battle, crippling the giant robot piloted by Peach and Kokone and triggering widespread destruction before being neutralized. This parallels his real-world physical confrontation with Kokone and her father at Shijima Motors headquarters, where authorities subdue and remove him after his scheme collapses. His ultimate fate following this confrontation remains unresolved.