First Appearance: X-51 #5 (October 1999).
Appearances: X-51 #5.
Years Active: 1945-present.
At the end of World War Two a Japanese scientist who had been working on a super-soldier serum (no doubt inspired by the effectiveness of Captain America (I) against Japanese troops and superhumans) discovers it but is forced to consume it to avoid having it captured by American troops. The scientist presumably gained superhuman strength, speed, and endurance from the formula, but no stories have been told about his activities, if there were any.
Similarly, his son(s) and/or daughter(s) are not mentioned as having metahuman abilities. The scientist's grandson, however, is Otomo, who as an agent of the Japanese government has been active fighting against cyborgs and giant robots, among others. Given Otomo's visible age (around 30), he would likely have been active as a Japanese hero for at least a year or two before the start of Fantastic Four #1.