Taizen Shiba

Taizen Shiba (大善 欺波, Taizen Shiba) is Yuuichi Katagiri's adoptive father who is presumably deceased, and is only mentioned throughout the series as "Sensei".

History
Taizen is presumably killed by Yuuichi Katagiri himself.

Yuuichi Katagiri
Yuuichi himself seemingly really dislikes it when people associate him with the "Shiba" name, even showing intense outbursts during those occasions.