Kamen Rider Ghost Episode 50

Takeru and the others go to Ryu's tomb to let him know that Takeru was able to revive. The Gammaizer menace is no more and everything has gone back to normal. Takeru has returned to school and is being helped by Akari to catch up with his studies. Alain looks up to the blue sky and makes a decision. Makoto, who with Kanon has seen off Takeru, lets his sister know of a decision of his own. A strange young boy holding a mysterious artifact appears and says: "The one with the power to change the world." What is the meaning of these words? The boy is attacked by the black Kamen Rider that appeared before.