Kazou was the son of Eiji Hasegawa. When Eiji was Oyabun of the Dai-Ichi Doku Clan, he was ordered to safely escort Manhunter (Mark Shaw), who was being hunted by Dumas, out of the country in fulfillment of his father's debt to Mark's father, Eliot Shaw.
Kazou next encounters Mark Shaw in Australia. The Dai-Ichi Doku Clan, still attempting to fulfill Eiji's vow of protecting Japan, believes the Invasion! alien craft which was auctioned on-line by Jeremy Heep can be of great use in keeping Japan safe. Kazou has vowed to bring the device back whatever the cost. However, the device is later activated by Jeremy and requires a "bioform" to function properly. When Jeremy proves to be an unsuitable host, the machine abducts Kazou, but Mark rescues him and takes his place thus incurring a Giri-Ninjo (a debt of honor that must be repaid). After helping to destroy the device, Kazou leaves.
When Kazou learns that there is a new Dumas, he flies to America to warn Mark and the Shaw family. As fulfillment of his Giri-Ninjo he promises to take the Shaw family to Japan for protection while Mark deals with Dumas II. However, Dumas II is at his home waiting for him and having just killed Kazou's father, Eiji. Kazou attempts to take revenge on Dumas II but is quickly disabled. Dumas II is about to kill Kazou but Ryu intervenes convincing Dumas II that Kazou is needed and he is made Dumas II's messenger after having the first segment of his pinky cut off. The family is held prisoner while Kazou returns to New York City to summon Mark. They both return to Tokyo with Kazou donning the Manhunter costume to fight Dumas and either slay him or distract him long enough for Mark to rescue his family. Kazou dies in the fight with Dumas II but his death, and that of his father's, are avenged by Mark Shaw.
- 9 Appearances of Kazuo Hasegawa (New Earth)
- 1 Images featuring Kazuo Hasegawa (New Earth)
- Quotations by or about Kazuo Hasegawa (New Earth)
- Character Gallery: Kazuo Hasegawa (New Earth)