Short flash animation series of Carole & Tuesday released on the official YouTube and Twitter channels.

Three sisters, Hozuki, Kazuki, and Hazuki, are descendants of Galileo and have completely different personalities and tastes; they never meet eye-to-eye. One day, the girls are suddenly attacked by a mysterious organization. The organization was after the "Galileo Tesoro" which Galileo Galilei was said to have discovered. Still unaware of what was going on, the sisters escape on the airship they built after the sudden attack. But it won't be so easy for these three sisters to help each other out in a pinch when they're constantly at odds with each other. What is the Tesoro, and what is the organization after? And what about the relationship between the sisters? It's a threesome of cute girls, action, and mystery!

Amaumi Haruhiko is a high school student who attends Shimano Academy in a town called Narasakicho. Narasakicho contains an unknown rainbow which constantly overlooks the town and is related to granting a magical wish called "Gift." Gift is a once-in-a-lifetime present between two people. As a child, Haruhiko has been close with his childhood friend, Kirino, until he obtains a new non-blood sister by the name of Riko. Haruhiko develops a strong relationship with Riko until they sadly depart due to the fact Haruhiko's father could no longer support the two of them. After some times passes by, Riko finally returns to the town of Narasakicho, and along with Kirino, starts to attend Shimano Academy with Haruhiko. The series revolves around the relationship among these main protagonists and slowly reveals the story behind both Gift and the rainbow.