Aliasing nise-akagi -> hirayama_yukio
His name is 平山幸雄 (Hirayama Yukio).
He is the "fake Akagi", but it is revealed in the same episode/chapter he first appears in that he is not the real Akagi_Shigeru. They tell you his name many chapters later, but the name is never of any importance.
Updated by jxh2154