Gabo

Background
Gabo fruit is actually a fist-sized red pumpkin fruitWN 1-6.

The quantity of the yearly harvest differ. Although the harvest area becomes smaller, they could be harvested in one month period and rarely fail. Furthermore it has a property that enable it to fertilize fallowWN 1-7.

It's the favorite food of Goblins, there was an explosive increase of goblins in the northern part of the kingdom, the scholar who investigated the cause concluded that it's related to Gabo fruit. In those days, if someone found a Gabo tree they would burn it down.

Seiryuu City
Gabo seems to be about 0.4-0.5 pennies a popWN 1-6.

There's a vast farm land harvesting Gabo, orphanage children works as farmers, the Gabo fruits the children harvest are actually staple foods for people with light wallets. It has strong smell, bitter, and hard to chew so the wealthy rarely ever eat it. Since you can eat cheap things until your stomach full, they're not only eaten by the orphanage children but also by about half of the general populace tooWN 1-7.

Thanks to Gabo fruit, the number of orphanages has increased dramatically.

It began to be used as a food source and now it has become the staple food of the lower strata people.