Tatsu was the wife of Maseo and mother of Yuki and Reiko. When Maseo's brother Takeo couldn't persuade her to choose him of her future husband, he became vengeful. As a criminal Takeo attacked Maseo's family with a special sword. While her husband and children were slain, Tatsu beat Takeo in battle thanks to her superior training in martial arts and claimed the sword for herself. While attempting to avenge her family's deaths as the vigilante known as Katana, she encountered Batman and other heroes in Marcovia and they formed the Outsiders. She eventually claimed victory over Takeo, though she never gained true peace in her heart, aside from that she found from mentoring the young Halo, her teammate. Katana did carve out her own legend, so to speak, as a heroine when tempted alongside other costumed crusaders.
Seiji (or the Anglicinized name of Sonja) was a young warrior for whose past not much is known. When first appearing, as a performer in an Asian show, Kato as Nightingale attempted to retrieve ancient artifacts stolen from Japan. But unlike Katana, Nightingale resorted to theft and murder leading to a few battles versus the Huntress. After this defeat, Sonia assumed a different alias as Judomaster in order to associate to some extent with the Justice Society of America.
This led to Kato evidently betraying that team, perhaps to exact revenge against Huntress who was member. Kato's cosmic twin on a composite post-Crisis Earth also served as a legacy member of that world's Justice Society. As a martial artist supreme, this Judomaster had something in common with the Judomaster of Earth-Four who was a Caucasian soldier Rip Dagger who fought evil during World War II. As for Katana, while she was also zealous towards protecting Japanese artifacts, for her the need for justice triumphed over that of vengeance unlike Kato.