28-year-old Manaka Mayu is a caregiver who works for ‘Himawari no Sato’, a facility for the elderly in Tokyo. She has been great friends with her grandmother Fumi since childhood, but has never met her grandfather, Toshiyuki, who was drafted as a crew member of the warship ‘Musashi’ shortly after marrying Fumi and died at war. Seeing her grandmother grow older year by year, Mayu feels a growing desire to learn what kind of person her grandfather was and also his last moments. Seeking clues, she sets off on a journey with Fumi and travels to Shikoku in search of Kiyama Mitsuo, a former crew member and a gunner in Toshiyuki’s squad on board the warship. They encounter a mysterious young man, Shinohara Toru, in Shikoku while looking for Kiyama. Although Kiyama had worked for the automobile factory that his nephew runs in his hometown of Oita Prefecture, he quit after his wife died of illness six years ago and goes on an annual pilgrimage of Shikoku. This is not only in memorial of his wife. There is a big motivation which he has never told anyone about. Kiyama has built an emotional wall and spent his remaining years quietly going on the pilgrimage. Then Toshiyuki’s wife and granddaughter show up. The facts that they are told by Kiyama is completely unexpected. The feelings of the four of them start to intersect now that the memories of 70 years earlier have been unlocked.