A Sister's All You Need

Itsuki Hashima is a popular, young novelist. However, he is obsessed with little sisters and his works seem to always include little sisters, so there’s some difficulty coming up with a new series. One day, his younger step-brother Chihiro and his colleagues, Hayato Fuwa, Nayuta Kani, and fellow college student, Miyako Shirakawa show up at his apartment. They enjoy dinner, drinks, and a game. That night, Nayuta makes advances towards Itsuki, but...

Nayuta and Miyako walk in on Itsuki, who was naked in front of the bathroom mirror, trying to act out the little sister character in his new volume. Itsuki is everything to Nayuta, and Miyako secretly has some feelings for Itsuki, but Nayuta also cherishes Miyako because she showed her compassion in her time of need. Nayuta invites Miyako to the hotel she’s staying at and immediately gets naked. She then asks Miyako to also get naked for some kind of research for her novel...

Itsuki, Nayuta, and Miyako have a hard time dealing with the cold and head down to Okinawa. The next day, they visit a remote island so Itsuki can do some research and Nayuta decides to flail around naked in the water. Miyako is awed by what she's seeing and eventually jumps into the water naked, as well. Two days later, Itsuki is invited by his illustrator to go to Hokkaido, where they try various local cuisines. However, Itsuki finds out that Setsuna had been ignoring a deadline...

Nayuta, Miyako and Haruto gather at Itsuki’s room for Valentine’s Day, and Haruto tries to show off his friendship with Itsuki again. Toki then shows up with the chocolates that fans had sent to them. A few days later, a new face shows up at Itsuki’s house. Itsuki was getting ready to do his final return for his taxes and all of his possessions are carefully inspected by the new figure...

Itsuki is nearing his final deadline for volume 5 and flees from his editor, Toki, however he is immediately caught. However, Itsuki manages to escape when he runs into Setsuna and they both go to a hot springs. Setsuna felt like he was in a slump and wanted to see some asses to get some inspiration. But when they get to the ryokan with the hot springs, Itsuki witnesses something horrifying...

Itsuki has a meeting with Kaiko Mikuniyama, the manga artist who will be doing the manga version of “Mahou Academy.” She looks very refined, which makes Itsuki nervous, but apparently she loves little sisters as much as he does. The group has a little celebration to celebrate the upcoming broadcast of Haruto’s anime and the manga version of Itsuki’s series. The group gets together once again to watch the broadcast of the first anime episode live, but…