Only A Mission

Amber the Hedgehog is Shadow's younger sister. They are very close, being there for each other, as family should.
They are given a mission to go to Earth and to collect the seven chaos emeralds tossed into Earth.
They are given Human forms and can always change back to their regular forms when they want.
They are forced to got to school, to blend in.
But something gets between them. People begin to grow suspicion towards them. They know that Amber and Shadow are not normal humans.