Akko and her friends are on summer vacation, and what could be more of a summer event than a beach trip? A festival is occurring around the beach, and while everyone is enjoying the festivities, Taisho and his gang head to a supposedly cursed island. Does Akko have anything to do with it?
Unfortunately the movie Akko-chan's Got a Secret! – The Sea! The Specters!! The Summer Festival is not yet available on HBO Max.
| Sound | Yūsuke Honma | Music |
| Visual Effects | Erkin Kawabata | Animation |
| Sound | Koorogi '73 | Theme Song Performance |
| Visual Effects | Nobuhiro Masuda | Animation Director |
| Directing | Harume Kosaka | Assistant Director |
| Visual Effects | Hidetsugu Hirayama | Animation |
| Visual Effects | Shinji Takeuchi | Animation |
| Directing | Takashi Hisaoka | Director |
| Writing | Hiroyuki Hoshiyama | Screenplay |
| Visual Effects | Kentarô Masuda | Key Animation |
| Visual Effects | Yoko Oto | Key Animation |
| Visual Effects | Hiroyuki Yokota | Key Animation |
| Visual Effects | Tomohiro Koyama | Key Animation |
| Visual Effects | Kenji Yamazaki | Key Animation |
| Visual Effects | Makoto Shinjo | Key Animation |
| Visual Effects | Nobuhiro Masuda | Key Animation |
| Visual Effects | Junichi Hayama | Key Animation |
| Camera | Isao Takahashi | Camera Operator |
