Magia Record Story Welcome to Uwasa Aquarium! ~ Entrust Your Memories to the Tamatebako
The following is a summary posted on 4chan's /pmmm/ general.
Sakurako learns that Ui dream of playing in the Dragon Palace with the Mikazuki Villa team, Touka, and Nemu. So Sakurako went to find a way to do so, enlisting the help of Ryo. Ryo convinced her to get Nemu and Touka's help since making them happy is the primary objective, and get Ikumi as well since she is an ace in the servicing sector. Nemu is just happy to see how Sakurako, a rumor who resist changes is trying to do so.
Sakurako promised Ikumi that she will make sure Yachiyo, Felicia, Sana and Tsuruno will also be well cared of and treated warmly, just like how she treat Iroha and her sisters in return for her help. Nemu helps with the details of Ryūgū-jō while Touka helps with tweaking the server Sakurako uses into said environment.
On that day, Mikazuki Manor team+2 and greeted with the marvelous site of Ryūgū-jō which is actually Sakurako's rumor space tweaked. It is like underwater, so Iroha need not fear of drowning, and Nemu can swim freely despite still not being able to move her legs. But Touka trio's dream of playing together in the sea is fulfilled as Touka and Ui hold Nemu's hand and guide her around.
Felicia and Tsuruno had great fun with the slide, Yachiyo enjoys a great seafood banquet while Sana gets her fun in the various cat idols decorated in the palace and a sandbed to build things with. Iroha enjoys the beautiful sightings on the slide moving slowly, eventually joint by the others.
Sakurako even read into how Felicia's love for action stuff, planning a hero show with Sakurako fighting her evil counterpart, complete with waving magic stick to empower her.
As Sakurako also got roped in, she felt joy as she see everyone having a great time, even overdoing it but allowing Sakura to bloom undersea.
As they went back, it seems letting flowers bloom was too much as Sakurako blacks out, making her feel fear from the sudden drop from being happy to losing everything.