Maou-sama, Sekai ga Oishi Sugite Horobosu no Oyameru.

The Demon Lord suddenly appeared in Saitama. Three descendants of heroes (a girl, a boy, and an old man) reluctantly (?) rise up to defeat the Demon King who has been resurrected to destroy the world. The heroes' only weapon is "delicious Japanese food." They must keep their stomachs full to curb the Demon Lord's destructive impulses!

(Source: Hero's Inc, translated)