Sword Art Online: Extra Edition
A fantasy series with the world-building and stakes that define the genre.
The story is set a couple of years after the events of Sword Art Online, where Kazuto "Kirito" Kirigaya and his sister Suguha meet up with Asuna Yuuki, Rika "Lisbeth" Shinozaki, and Keiko "Silica" Ayano at the SAO Survivor School. Kirito then attends emergency counseling, while the girls go for a swim at the pool. It turns out that said "emergency counseling" is a subterfuge set up by Seijirou Kikuoka, aiming to rehash the incident of Sword Art Online in hopes of determining Akihiko Kayaba's motives. What will the girls get up to in the pool, and what awaits Kirito and his "counseling"?
Plot summary from MyAnimeList. Data and images via Jikan API.