"When a person from one world enters another," the stranger began, "he carries within himself the very essence of the world he came from. That essence can sometimes transfer over, depending on what the person does. Different worlds interact with each other in different ways."
He paused, making sure Naruto understood. The look on Naruto's face showed comprehension. The whole affair felt like a chore, but he still took it seriously. He felt responsible for his world and its well-being. Hokage behavior, you could call it. Kurama smirked with pride.
"I can only assume things from my world tend to cross over into yours pretty quickly," the stranger continued.
Naruto knew what he was talking about—he had already foreseen this exact moment, only seconds ago.
"That little peek you get into the future," the stranger explained, "is my Observation Haki. It lets me see moments ahead. Since I arrived here, Haki has become a reality in your world—through your interaction with me. And because you possess tremendous power, it has latched onto your chakra as a placeholder, letting you wield it as I do."
Naruto nodded. The first time he had used it was in battle, when he had no time to think about how or why he was seeing the future. Now it finally made sense.
"Chakra in our world is the closest thing to Haki in yours," Naruto said. "And with the vast amount I possess, your techniques are transferring over to me. Am I correct?"
"Sort of," the stranger replied, pleased with Naruto's reasoning. "These crossovers happen unpredictably. There's no exact way to know how the reality of my world will spill into yours. There are some patterns it usually follows, though—like physical proximity and interaction. Since I'm close to you and we've interacted in significant ways, more of my world has transferred into you. This means not everyone in this world can use Haki or see into the future. For now, it's just you.
"Another guideline is knowledge. The more you know about me or my world, the greater the transfer. That's why I haven't even revealed my name."
Naruto scratched his head. He knew there was more to it.
"But," the stranger continued, "I have shared plenty of information about Haki itself. That might increase the transfer—but I needed you to have this knowledge. You'll need it for what I'm about to ask you to do."