There were five of them at first. Tetsuko, Tetsuya, Tenshi, Tenri, and Terumi were their names in birth order. They all were normal children until they hit five . That was when they were secretly classified as child geniuses.
The very next year, their month-younger cousin Tora was given the same classification. Her parents didn't want to deal with the problems of a genius child, so the quintuplets' parents adopted her and she became one of their children instead.
In the next six years they grew abnormally fast, easily being mistaken as a first year middle schooler when they were eight. Their IQs didn't help in the matter either, as they could easily blend the older children. So they hid their identities and age.
The middle school they went to required them to be in an extra curricular activity, they chose to enter a intermixed gender basketball club in the first year. They easily became the starting regulars.
Under the surname Shiroko, the Kurokos, with Tetsuko as their leader and their Tetsuya as the second-in-command, won every competition they entered. They became known as the "Athletic Royals," especially since the child geniuses were recognized to come from a wealthy family.
Everything changed after their last Winter Cup when they were eleven. One by one, their bodies began to fail until they could barely move and was forced into a coma. When they woke up two months later, the memory of basketball and their middle school years were erased from their minds. A symptom that their bodies grew to fast that they were physically unable to handle it.
The grandparents decided to withdraw them from the public eye as they began to recover. The five siblings and their cousin were separated. The second-born child was sent with the parents to live in Tokyo. The three middle children were taken to live in the country side of the United States with the grandparents while the oldest child and their cousin were sent to live with their grandfather's sister.
Five years later, the siblings and cousin are reunited. What is going to happen?