Ninja - Benedict Jacka

Running away from home is usually a bad idea. However, Ignis, Allandra, and Michael have three good reasons for doing it. First, their father Vargas Havelock is a drug baron; second, he's thoroughly evil; and third, he
expects them to join him in the family business before they get much older. Given all that, running away starts to look quite reasonable.
But when Ignis and Allandra stage an escape during a holiday in Wales, taking Michael with them, things don't go to plan. Michael gets recaptured, and Ignis and Allandra nearly drown. When they wake up, they find they've been taken to a secret valley deep in the forest. A school is hidden there, built into the treetops, and it's filled with children studying to be ninjas. This is Rokkaku, and it's to become their home.
And so Ignis and Allandra's new life begins. The ninjutsu training is hard, but the friends they find make up for it. Outside Rokkaku, though, Vargas is still looking for them. Sooner or later, Ignis and Allandra are going to have to face their father again . . . and their brother too.