Awesome educational manga set in a medieval\fantasy world. It starts with a hero who is about to fight and kill an end boss, however instead of fighting said end boss, the hero sides with his enemy (this sounds somewhat familiar*). Together they try to make the world a better place using economics, education and improved agriculture. There is also a hint of romance, since that end boss was actually a woman.
Interesting aspect of the manga is the fact that characters are semi-symbolical. In fact, Maoyuu Maou Yuusha characters don't even have names. It was common practice in literature of the past to include representatives of each social class among its cast. This is taken a level further in Maoyuu Maou Yuusha, think something like Hetalia's characters. An example of that symbolism would be this: The protagonists teach a son of a noble, a son of a warrior and a son of a trader. It doesn't necessarily mean they are teaching only 3 people, most likely it means they are just teaching the next generation of nobles, warriors and merchants. It's just that this next generation is shown as 3 people.