Seimei Kikan

Seimei Kikan (生命帰還, Life Return) is a technique known only to CP9 members Kumadori and Rob Lucci.

"At the sea for a thousand years, and at the mountains for a thousand years, breathing the wind and drinking pure water, he passed the training of a Sennin. Enduring it all, he gained the Life Return. Humans are able to, from the hair on their head to their intestines, their toes, even to their most minute hairs, to concentrate their senses and stretch them to their limits, making it possible to control every part of their bodies."

— Kumadori, CP9

Given Kumadori's flamboyant nature, the parts about a thousand years at the sea and mountains, are likely exaggerated

He demonstrates this when he was able to eat all the food within a giant refrigerator, digest all the food and most of his body fat, turning him super-skinny, then absorb all the nutrients in the food turning him back to his original size. He also uses Life Return to use his Hair Bind, in which he controls his hair to trap his opponents or form hands to perform Shigan with. For some reason, when Chopper roared in Monster Point, Kumadori couldn't control his hair temporarily and it froze where it was before returning to him.

Somehow, Rob Lucci also knew and utilized Life Return. He only used it in conjunction with Kami-e to make his half-leopard form smaller and more maneuverable. It is unknown how Lucci was able to use Life Return. It is also unknown if he has the same level of mastery as Kumadori, as he has yet display it.

Urouge of the Fallen Monk Pirates and the Eleven Supernovas, has shown to expand his muscles at an accelerated rate. This ability is speculated to be either Life Return or a Devil Fruit.

It is also possible that Jewelry Bonney of the Eleven Supernovas possesses this ability, as she is capable of consuming copious amounts of food without gaining an ounce in visible weight.