Yoshioka is a member of Souichiro Takagi Ultra-Nationalist Organization in Tokonosu Prefecture.
Yoshioka is a retainer of the ultra-nationalist group in Tokonosu Prefecture that is lead by Soichiro Takagi. When the city was over run by Them (zombies), the Takagi Estate was used as a fortress and shelter for the group and any survivors they could find.
Yoshioka is a supporting character of the manga/anime series Highschool of the Dead that was written by Daisuke Sato and illustrated by Shouji Sato. The series first began serialization in Fujimi Shobo's Monthly Dragon Age magazine in July 2006.
His first appearance was in Hightschool of the Dead Volume 3 CH. 11 "The Dead's House Rules", and his first anime appearance was in Highschool of the Dead - Episode 10 "The Dead's House Rules". His character in the Japanese series is voiced by Takaya Kuroda , and the U.S. dub produced by Section 23 is performed by Chris Ayres.