This series is quite obscure outside of Japan, but we can read a short plot description on Amazon Japan (“translated” with Google Translate):
“Tetsuma Kan, a peasant’s prisoner, is a bad guy who is entitled “Bonno” because of the annoyance of missing digits. In 1938, he committed the only daughter, Takako, of the landowner Ishikura, and jumped out of his hometown to climb to an equal position with Ishikura’s house. One generation of a man who lives in a turbulent era and rises to the top of politics.”
We can assume the game would have followed the same storyline, but not much is known about this project. Heimao found a single screenshot from the game in an old gaming magazine and shared it on Twitter.
As it often happens with cancelled Famicom games, today Ooinaru Kan is forgotten by everyone and we’ll probably never know more about what happened to it.