I'm in One Piece, but the System Wants Me to Learn Ninjutsu?

Feng Lei transmigrated into the world of One Piece, only to be bound to a Ninjutsu Learning Genius System.

"Come on, System, this is the world of pirates! Pirates! Where am I supposed to find Ninjutsu?"

Then Feng Lei began learning the Six Powers under Garp's tutelage.

[Host detected learning Taijutsu. System assessment: This Taijutsu is the Eight Inner Gates!]
[Acquired Ninjutsu: Eight Inner Gates.]
[Eight Inner Gates: Learning progress 1%.]

"Wait, you're calling this the Eight Inner Gates?"

It was as if Feng Lei had discovered a whole New World, and from that day on, he set foot on a path to the very heavens!

He watched the Flame-Flame Fruit's power in action.

[Host detected learning Fire Style...]

He watched the Combine-Combine Fruit's power in action.

[Host detected learning Susanoo...]

He watched the Woods-Woods Fruit's power in action.

[Host detected learning Wood Release...]

At Marine Headquarters, Feng Lei opened the Eight Gates, summoned Susanoo, and unleashed Sage Art: Wood Release: True Several Thousand Hands. "From this moment on, I will bring the Great Pirate Era to an end!"

[This synopsis doesn't do the story justice, so please give the main text a try. Thanks for your support! You can count on this veteran author's integrity!]