Tonbo!

Having lost the family and job, Igarashi flees society to Hinoshima, “Japan’s last hidden paradise” and meets Tonbo, the island's only middle schooler. Igarashi senses a pervasive golf theme on the island despite no course or known golfers on the island.

While visiting a golf course on the island, Igarashi witnesses Tonbo's incredible super shot and Tonbo is intrigued by Igarashi's golf skills. Gon encourages Igarashi to experience the island's starry sky, under which Tonbo reveals her past.

Tonbo impresses Igarashi with her unique style with a 3-iron. Intrigued, Igarashi adapts his wedge with her 3-iron's grip. Teaching Tonbo reminds him of instructing his son, Rintaro, evoking regrets about robbing Rintaro of golf's joy.

Igarashi observes the interactions between Bunpei and Yoko. Golfing daily with Tonbo, he wants her to try tournament golf. However, he feels there's something unusual about her play. Unexpectedly, a squall hits them on the course.

Igarashi's unease with Tonbo's golf stems from Tonbo not feeling the pressure of competitions, but Tonbo's actions make him reconsider. Learning from Yoko that Tonbo hates leaving the island, Igarashi realizes that a change in perspective is needed.

Igarashi heads to Kagoshima to find one who can match Tonbo but failed. He learns that Yoko’s niece is a junior tournament winner. So he arranges her visit to Hino Island. Days later, a pickup truck arrives by ferry, with the girl sleeping in the back.

Despite meeting for the first time, Tonbo and Tsubura decided to play a round on the island's golf course. Inspired by each other's contrasting styles, a competitive spirit grows within Tonbo, determined not to lose.

During a typhoon on Hinojima, Tonbo and Tsubura took refuge. Despite the power outage, Tsubura practiced her swings and shared her feelings. After the storm, she gave Tonbo her 5-wood. Igarashi found a hidden golf hole and took Tonbo to play it.

Igarashi goes to Akureki to meet Mr. Kuta, designer of the Hinonoshima golf course. He shares his past with Tonbo, who fears leaving the island. The next morning, Tonbo joins him. Mr. Kuta shows them a special one-hole course in the forest near a pond.

Mr. Kuta's single-hole course on Akureki Island was a challenging monster hole. Igarashi struggles with it, while Tonbo impresses with creative shots. However, Mr. Kuta has doubts about Tonbo using a 3-iron for putting.

Mr. Kuta insists Tonbo's golf style won't work in competition and takes them to a challenging practice green. Tonbo spends the day tackling it, growing to appreciate Igarashi and Mr. Kuta's kindness.

After Akurekijima, Tonbo penned "The Last Summer Vacation" essay, expressing love for the island and resolutions. Islanders were surprised; Igaiga supported her. By spring graduation, Tonbo grew taller, hair reaching her shoulders.

Tonbo's decision to leave the island deeply affected the nearby residents. Amidst mixed emotions, a farewell golf tournament was held with just one day left until her departure.