Behind Shea and Wada's house is a mysterious tower. Access to the building is restricted by a statue blocking the doorway inside of their house. To permanently remove the statue, give Wada gifts until he reaches at least 7 hearts (40,000 FP). You also need to be in your 3rd year of the game or later.
Once you have met the requirements, go into Wada's house to unlock the event. Wada will declare friendship with you and lets you access to their sacred tower.
The blue Harvest Sprite, Manfred, will move to the base of the tower after you gain access to it. Every day he will reward you with a food item. It could be just a basic crop, recipe ingredient, or even a fully cooked dish. The item he gives is random, and you can always save your game before talking to the sprite and then simply reload to try again if you don't like the item he gives you.
The advantage to unlocking the tower, besides free food, is you can acquire crops that you might not have unlocked at Chen's store yet. For example, you have to ship 100 pieces of Wheat in order to unlock Cabbage seeds. If you are lucky enough to receive a Cabbage from Manfred, and you have the Seed Maker, you can convert your little Cabbage into a bag of seeds for planting, without the need to ship all that Wheat.