Who's This? One of many martial arts characters in Who's Who vol.XII, he's the one on page 3.
How you could have heard of him: He was the father of Checkmate's Tommy Jagger, and enjoyed a handful of flashbacks in the past few years (Detective Comics #723, Blue Beetle #8, All-New Atom #14) and a small role in Infinite Crisis that ended with his being killed by Bane.
Example story: Judomaster #92 (1966)
But let's not get ahead of ourselves. The issue starts with Rip returning to base from the previous issue's events, with a young Japanese orphan who's stowed away on his plane. Though he's earned the nickname Tiger (that's what the narrator calls the readers too) and knows Rip is secretly Judomaster, the hero won't let him tag along on his adventures. Off to the orphanage for you! But Tiger runs off and tries to help Rip as he pursues Nazi agents, and is taken hostage by the bad guys.
Who else? Jonny Double was saved from obscurity by his Vertigo mini-series, so where I go next depends on whether I want to infuriate Who's Who fans by mounting a defense of J. Wilbur Wolfingham or not.