Twilight of the Dark Master: Tsunami is an ancient guardian from days long ago when the Mother Spirit created demons and guardians to aid a fledgling human race. In 2089, only a few demons and guardians remain in the city of Neo-Shinjuku. Tsunami becomes involved with a woman who has just lost her fiance and her arm and now wants to figure out why this has happened. Meanwhile, the demon leader is still alive and plotting to enslave mankind.