訓練所のサンドバッグおじさん、実は最強でした ～クビになった途端、出世した元弟子たちに迫られるのだが～

あらすじ

Lyle is a lowly unemployed middle-aged man who was fired from his job as an academy instructor after being turned into a "Sandbag" even by his former trainees. However, that old-fashioned "Sandbag Tactics" is actually the strongest──!? Why is he so strong even though he's a "Sandbag"!! The epic tale of an unemployed, unknowingly strongest middle-aged man's rise to the top!!