The recent One Piece flashback mini-arc is over. Fans now know the life story of Bartholomew Kuma as it pertains to the events of the Egghead Arc. The arc was enlightening regarding his relationships with other characters on the island, including Jewelry Bonney, Dr. Vegapunk, St. Jaygarcia Saturn, and, in a way, Admiral Kizaru and Sentomaru. When human, he needed Vegapunk to cure his daughter's disease, but St. Saturn intercepted the bargain and forced Kuma to become a cyborg as a stipulation. This process would cost the Buccaneer his free will and the chance of seeing Bonney again.
Source：https://www.cbr.com/one-piece-chapter-1103-kuma-egghead-role/
