Ryuji (Taisho Iwasaki), Satoru (Ryuga Sato) and Atsushi (Hidaka Ukisho) are friends in high school. They are classmates in the 2nd grade class B. They appear like troubled students, but they are not. They are actually country boys.

When they are at their secret place, they suddenly feel a big shake and hear the sound of thunder. Then next moment, they see a man Sanpei wearing a dirty military uniform with a backpack and holding a bayonet. Sanpei came from the past, right before the end of the war in Guam. Ryuji, Satoru and Atsushi enjoy their time with Sanpei. They think that being with Sanpei, their lives might change and they ask him to spend summer with them. Class President Michifumi (Yuto Nasu) and twin brothers Akihiko (Naoki Fujii) and Kazuhiko (Issei Kanasashi) join the group.

本片以关东地区某省会城市的一个卧室小镇为背景。住在这里的高中生风间龙二（岩崎大正饰）、濑名佐渡（佐藤龙也饰）、柴山道人（那须悠人饰）、春日敦（啄木鸟翔饰）、山田明彦（藤井直树饰）、山田和彦（金崎一成饰）等人，在战争结束时遇到了从大宫岛（现关岛）穿越而来的士兵三平。故事由此展开。

　　在来自一切都不方便的时代的三平眼中，战时的三平所看到的现代日本和年轻人（龙二、佐藤、道文、笃、明彦和和彦）的世界是什么样的呢？　今天的人们自以为享有自由。但谁真正拥有自由？

　　影片通过这些各有各的境遇的高中生以及与他们一起工作的士兵的生活，向世人提出了一个问题：什么是真正的幸福和真正的自由？

지방도시에 사는 고교생들이 1945년의 괌에서 타임슬립해 온 군인과 만나 펼치는 한여름의 성장 이야기