actors during breaks to watch them train. Tak Sakaguchi was cast as Zeros by Kitamura, feeling that Sakaguchi would be able to make the character look "cool." Kitamura wanted to "utilize" Sakaguchi's facial features and went through several designs until the crew achieved the final look. Various versions were rejected for the film's title logo, feeling that some versions resembled the title logo for Alien. Writing Kitamura intentionally did not specify the time frame or setting of the film, wishing for the film to be universal. The film originally began with Tenshu being executed by hanging but Kitamura found the idea "too tacky" and decided on an electric chair instead, feeling that an electric chair was "cooler". Kitamura created the character Zeros specifically for the film in order to have Tenshu battle an equally matched opponent for the film's climax. Kitamura described Zeros as a character that was cloned from the Isomer and human DNA. He also described Zeros as a character who spent his life among machines, being plugged into devices and injected with mysterious chemicals. Earlier drafts had Zeros explode due to Tenshu's psychological waves and was intended to be the film's visual effects showcase, however, Kitamura rewrote it after feeling the scene wasn't going to be "enough" and didn't do Zeros "justice." Kitamura wanted to give Zeros a "Frankenstein-like" quality, to be "pitied" after the Isomer is taken from him. For the film's ending, Kitamura wanted the film to end in a "climactic" way without it being an action scene. In the manga's opening, Tenshu broke down after the faux electrocution, however, Kitamura altered this idea by keeping Tenshu emotionless, stating, "I wanted to hold off showing Tenshu's weakness until later." Gondo's psycho nature was added specifically for the film. Filming The execution scene in the film's opening was filmed near the end of principal photography. A scene was filmed that had Tenshu being led down a giant corridor after the execution scene. The corridor was 150 meters below ground, under construction, and 5 cm, which prevented the crew from bringing enough equipment. As a result, Kitamura was dissatisfied with the way it looked and cut it from the film. The prison hallway scene was filmed on April 27, 2001, on the roof of Yokohama arena. The tunnel at the film's climax was filmed at the Kasukabe Drainage Canal, which was under construction during principal photography. The