While in the military, Watanabe allegedly ordered one man who reported to him to be punched in the face every night for three weeks and practiced judo on an appendectomy patient.

Prior to the 1998 Winter Olympics in Nagano, the CBS News program 60 Minutes interviewed Watanabe at the Hotel Okura Tokyo as part of a feature on Louis Zamperini who, four days before his 81st birthday, was returning to carry the Olympic Flame torch through Naoetsu en route to Nagano, not far from the POW camp where he had been held.

[2] Accounts of Watanabe's abusive behavior are given in Laura Hillenbrand's book about Zamperini titled Unbroken: A World War II Story of Survival, Resilience, and Redemption (2010).

In 2014, Japanese musician Miyavi played Watanabe in Angelina Jolie's Unbroken, the film adaptation of Hillenbrand's book.

[4] David Sakurai portrays Watanabe in Harold Cronk's Unbroken: Path to Redemption, a "spiritual successor" to Jolie's film, released in 2018.