Yoshika's father was the genius behind the Striker units—the magical technology that lets the Strike Witches take flight and fight the Neuroi. Mio Sakamoto was actually the first person to test-pilot his invention. But here's the thing: Yoshika had no idea about any of this. Her dad vanished when she was ten, and she grew up in the dark about his work.
The lab where he developed the Strikers was destroyed in an accident—a bad one. The building went up, and everyone assumed he died in the explosion. It's a tragic origin story that shaped who Yoshika became, since her father's whole philosophy was about using whatever power you have to protect the people around you. That belief stuck with her, and it basically defines her character throughout the series.
Content compiled by AnimeList.moe from publicly available sources.
