Professor Yumi runs the Photon Power Research Laboratory and is best known as Sayaka's father—he's also the one who built her robot, Aphrodai A. He goes way back, having worked alongside Kouji's grandfather Juzo.
Interestingly, the newer series Shin Mazinger Shougeki! Z-Hen switched up his first name to Yannosuke, breaking from basically every other Mazinger show that called him Gennosuke.
Content compiled by AnimeList.moe from publicly available sources.
