High-schooler Ryoma Mikoshiba finds himself summoned to another world by the warmongering O'ltormea Empire. But Ryoma is no ordinary school boy – he has both talent and training in martial arts. Using his skills in martial arts to escape captivity and swearing revenge on the country that summoned him, Ryoma finds himself in a world where he can become stronger by absorbing the life force of whomever he slays – a…