2. Hidden Power
When Ryosuke meets Lisara, she winds up stabbing him with half of a supernatural, practically all-powerful sword known as Graham. Neither of them know that the other half is already inside him, so later when he releases a huge blast killing one of the monsters, they realize that the other half is inside him. Eventually, they find out from his mom, via video chat, that his dad had placed the second half inside him, which means that Ryosuke actually is half Shinigami himself, although it isn’t specified. But because Lisara put the hilted-half inside Ryosuke the blade becomes whole again.
Issei dies as a human not knowing that there is a dragon in his left hand. (Writing it down like that sounds weird, but its true.) At first no one really knows that it actually is Draig, the Dragon of Domination. At first, he is told his power is simply known as “The Dragon’s Hand,” and that it is able to boost his strength for a short time. After his first major fight, his “Dragon’s Hand” evolved into something better. When Rias sees his new look, its very obvious that he has the actual Dragon within him. As the series progresses and Issei trains, he is able to unlock more and more dragon like capabilities.