Nagasaki in 1986. Hisada, who lives with her affectionate parents and her younger brother, although there are many quarrels between couples, is a fifth grader who loves Yuki Saito and Exogini. Hisada decides to go to Boomerang Island to "see the dolphins" with Takemoto, whose house is poor and avoided by his classmates. Drowning in the sea, getting entangled in the Yankees, and having a lot of trouble, but as the friendship between the two deepens as a result of this adventure, a sad incident that presages farewell occurs.
| Directing | Tomoki Kanazawa | Director |
| Writing | Tomoki Kanazawa | Screenplay |
| Writing | Jun Hagimori | Screenplay |
| Production | Michi Iijima | Executive Producer |
| Production | Mitsuru Sato | Producer |
| Production | Tamotsu Osano | Executive Producer |
| Production | Jun Takahashi | Producer |
| Production | Tomonori Fukuda | Line Producer |
| Camera | Yusuke Suga | Director of Photography |
| Editing | Narihiko Kôno | Editor |
| Costume & Make-Up | Reiko Matsushita | Costume Designer |
| Art | Takuya Okada | Art Designer |
| Sound | Kotaro Marubashi | Music Producer |
| Lighting | Yamato Watanabe | Lighting Director |
| Sound | Masaharu Tanabe | Sound Recordist |
| Art | Takayuki Sato | Set Decoration |
| Costume & Make-Up | Asako Nagashima | Makeup & Hair |
| Crew | Emiko Togawa | Script |
| Directing | Kazuya Shintani | Assistant Director |
| Directing | Dan Ogawa | Assistant Director |
| Costume & Make-Up | Kayo Hosomi | Hairstylist |
| Sound | Michiru Oshima | Original Music Composer |
