Kanchigai no Atelier Meister

One day, Kurt, a kind-hearted boy, is suddenly kicked out of the Hero's Party for being “useless”. He finds that his aptitude for weapons, magic, and all other combat-related skills is the lowest rank, so he takes odd jobs repairing the castle walls and digging for minerals to make a living, where his exceptional abilities are immediately revealed. He proves to be skillful in cooking, building, mining, and crafting magical tools.

In fact, his aptitude for every skill unrelated to combat had an SSS ranking! Kurt, however, seems completely unaware of his talent and ends up saving people, the town, and even the country through his unaware actions.