Their is Steven Universe son of Pink Diamond. Everyone thought he is the only half gem/diamond, but in fact he isn't the only one or even the first one. There is another half diamond/gem more powerful and deadly. His name is (y/n) Black son of Black Diamond who was the first and most powerful diamond of all time. (y/n) wanted to know more about gems and any possible relatives of his mother's side. One day he found out about beach city and unnatural stuff happenings for years. How would (y/n) like it seeing his cousin and other gems?