Her name is Yu, but she calls herself Ah Xi. She has been living in the laboratory and knows nothing about the outside world.
His name is Chrollo, he has great ambitions, but he was captured by a mad scientist. In the iron cage, she was the only one special, and he wanted to get to know her.
The laboratory exploded and they escaped, but fell into another force and couldn't help themselves. However, fate has always been in the hands of those who are unwilling to give in, so the Phantom Troupe was established.