Yomigaeru Kinro (1999)

Asakura Tetsuya is a man who leads a double life. By day, he is a mild-mannered and affable salaryman in the Mogi Corporation. Come night, he takes on the persona of a hardened and violent individual bent on exposing the shady dealings of his company. Tetsuya’s brother was a former president of one of the Mogi subsidiaries, but committed suicide under mysterious circumstances after some company trouble. Tetsuya is convinced that acompany conspiracy staged the suicide, and he is obsessed with finding out the truth in order to avenge his brother. (Source: IMDB)