Trying to move on in his life, former professional golfer Kazuyoshi Igarashi arrives at Hinoshima Island for a job at its development center. Expecting the island to be a very rural area with nothing much to offer, Kazuyoshi cannot hide his amazement when he discovers a complete golf course made by the island's inhabitants. Using the seaside terrain to their advantage, the people there have adopted golfing as their hobby. To add to his surprise, Kazuyoshi meets a young girl named Tonbo Ooi, who has been playing golf using only a 3-iron—a notoriously difficult-to-use club. As the former pro gets more involved with Tonbo and witnesses her seemingly impossible shots, he begins to see golf in a whole new light, rediscovering how fun the sport can actually be.

After graduating middle school, Tonbo Ooi sets sail from the isolated island of Tokara to Kumamoto in hopes of advancing her golf career. Using his connections, Tonbo's mentor Kazuyoshi Igarashi is able to convince coach Hajime Udou to train her. While Tonbo initially has trouble showing off her abilities with her peculiar playstyle and inexperience with using a variety of golf clubs, she quickly proves her worth at her course debut by making use of her unique skills. Leaving an impression on Hajime and the people around her, Tonbo is sent to compete in the Kyushu Women's Championship. Met with familiar faces and new rivals, she is determined to dive deeper into the professional world of golf.