One Piece: Reborn in the Mink Tribe as Admiral Tom Cat

After transmigrating into the world of pirates as Siro of the Mink Tribe, he awakens a Tom the Cat roleplaying System. Completing the System's missions and spending money lets him raise his roleplaying progress, improve his Haki, and grow stronger.

When his roleplaying progress reaches sixty percent, he unlocks five abilities: immortality, super strength, super speed, scientific genius, and shapeshifting. Siro plans to join the Marines and coast along, but to his surprise, Sengoku directly promotes him to the fourth Marine Admiral, codenamed Blue Cat.

From then on, the Marines have a monster of the highest order in their ranks.

Akainu: “Why the hell is this cat completely unharmed after my magma burned him to ashes?”

Kaido: “If anyone calls me the Strongest Creature again, I'll kill them with a Thunder Bagua! Siro outclasses me in strength and speed, and he's immortal. He's the true Strongest Creature on land, sea, and air!”

Red-Haired Shanks: “I asked him to show me some respect, and he smacked me right in the face! I'm one of the Four Emperors. Don't I deserve some respect?”

Imu: “Siro has the perfect immortality I've always dreamed of. His fighting style is even freer than Nika's. I must have his power!”