Tomorrow's Dawn
Heroes Never Die
If I remember correctly, throughout Japanese history, especially in the Kamakura era from what I recall, despite having a centralized government and singular capital, oftentimes samurai and different clans would directly war against each other for favor of the emperor. I think that this personifies city-states best for Japan.
The Genpei Wars (Minamoto-Taira) come to mind especially.
But yes, I stand by Warring States for Japan running City States.