Reborn for the second time, he ends up as Shinji Matou's son and has to face the challenge of surviving on his own as a newborn.
He originally planned to take part in the Fifth Holy Grail War, only to discover that the Holy Grail War in this world is bizarrely different: the Fifth Holy Grail War has become the First.
The most unbelievable part is that Ryo is only four when the Holy Grail War begins.
He wanted to live an ordinary life, make money as a writer by copying other people's works, but someone handpicked him to go to Chaldea.
So Ryo, the Golden Saint who has no choice but to fight for humanity's future, raises his fist and tells the summoned Servants:
"Everyone, stand back. I'll handle this!"
