二度目の人生はスキルが見えたので、鍛えまくっていたら引くほど無双してた件 (Associated Names)

One day, the protagonist, who worked at a so-called “black company” doing simple tasks of typing text from early morning to late at night, died of exhaustion due to lack of sleep. He overworked himself and deprived himself of sleep. Then, he found himself back 20 years ago, when he was six years old. A…