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?

Alcia is a world governed by Count: numbers engraved on a person's body, representing any number related to their life. These Counts determine a person's social status and power in Alcia. If a Count reaches zero, the person is sent to the Abyss, a place rumored to be worse than death. Hina, a traveler whose Count is based on the distance she traveled, witnessed her mother get dragged down into the Abyss. Determined to fulfill her mother's last wishes, she sets off on a journey in search of the legendary Aces—heroes of the war that happened three hundred years ago, bearing a white star next to their Count. While wandering around, Hina encounters Licht Bach, a mysterious masked man with negative Count, and Nana, the owner of a tavern. In the midst of having a good time, Hina is tricked into a battle with a military soldier. However, despite his negative count, Licht rescues Hina and reveals that he has another count, one with a white star, one of a legendary Ace. Plunderer follows the journey of Hina and other inhabitants of Alcia as they discover the truth about their world, the Abyss, and the legendary Aces.

Naoya Mukai is having the time of his life after his childhood friend Saki Saki finally accepts one of his countless confessions. Ensuring that their relationship will stay strong, he spares no effort in showering affection to his now beloved girlfriend. However, one afternoon, another girl named Nagisa Minase suddenly confesses to Naoya following months of preparation. Even though he politely rejects her, Nagisa's irresistible charm and determination continue to attract Naoya. Wanting to fulfill both Saki and Nagisa's desires, Naoya ends up proposing a crazy idea—to date the two of them simultaneously, with both girls fully aware. This unprecedented state of affairs ultimately causes wacky and hilarious situations in whatever they do to keep their unusual relationship going.

Hikari Hanazono has always been able to do things that normal people cannot. As a child, she assumed no one could beat her—until she met Kei Takishima. Thinking she would win, Hikari challenged him to a match. But things didn’t go as planned; she lost not once but each time she rechallenged him. From that point on, she has sworn to best Kei at everything, ranging from academics to athletics. To achieve her goal, Hikari enrolls in the same school as Kei—Hakusenkan, a prestigious institute for the wealthy. As a pair, they hold the top two rankings in school and are among seven of the academy's best students in a class known as Special A. While Hikari treats Kei as a rival, she is completely oblivious that he harbors hidden feelings for her. Together, the members of Special A deal with competition, friendship, and just a bit of love.