Time flies by; Hiroyuki and Akari are 12th-graders now. Both of them and their friends have grown up gradually in someway, physically or mentally, but one of their best friends is missing: the lifelike android Multi. To their surprise, Multi is brought to their campus again without notice, yet she is no longer the same Multi they have known.

Wataru Minakami is a top student who failed his high school entrance exam because of a computer glitch. He later discovered that he was accepted to Stargazer Hill Academy, which is located at a mysterious place called Promised Island. At the request of his father, Wataru is whisked away to the island, and before he can settle in, a dozen of cute and charming girls start to flock him and claim to be his younger sisters. As Wataru gets closer to his newfound siblings, a deeper mystery as to why they were sent to the island comes to play. (Source: ANN)

This OVA is divided into two parts. First one is about Torii Shoutarou following his younger sister on a date. Second one is about Christmas Eve, which Mitsuki, Yuuya and their friends spend at Kanzaki's house. Bundled with the limited-edition volume 7 of the manga. (Source: AniDB)

The series will depict college students as they prepare and participate in a RoboMasters tournament.