Naruto: Systematic Shinobi - Chapter 26: Waterfall 5

Failing in his job hunting, Sanada Kyouichirou was hopeless in this society. When kyouichirou had thrown himself towards the bottom of a cliff. When he woke up his body had returned towards when he was in fifth grade of elementary school. He did not want to have any regrets in this life so he had decided on building up an harem in this second life.

The elder sister that he admired, a senior and president of the student council at a school for rich young girls, a strong minded upper classman at school. The poison fang of Kyouichirou who had pretended to be a innocent child attacks those girls.

A failed investor from 2017 got drunk and woke up in the 1980s. China is just opening up, and the economy is blooming. There is also the dissolution of the Soviet Union, the bursting of the Dot-com bubble and other financial crisis. He used his knowledge of the future and slowly build up his empire.

- Description from novelupdates

Klein’s greatest wish is to transmigrate to another world and live life in an isekai, just like in anime, manga and novels. However, fate is on his side and the typical truck that the main characters always carry in isekai runs over Klein. But, to his bad luck, he lived a few more days in the hospital and, just on the day he died, Klein heard a ⟨⟨-DING-⟩⟩ that he knew it meant. That was the day of his death, but also the beginning of his adventure into another world.