WARNING: The following contains spoilers for One Piece Chapter #1020, "Robin vs. Black Maria," by Eiichiro Oda, Stephen Paul and Vanessa Satone, available in English via Manga Plus and Viz Media.
Following his dramatic throttling from Kaido during the ongoing Onigashima Raid, Luffy has regrouped with Momonosuke and Shinobu in the One Piece manga. But they are being watched from the sidelines by one of the series' more unexpected characters. Caribou, who previously sought to destroy the Straw Hat Pirates, is spying on the meeting from behind a tree in Chapter #1020.
He's initially confused as to why Luffy isn't on Onigashima and thinks to himself that he'll never escape the island if the Straw Hat doesn't "get it together." What this means for his role in the battle to overthrow Kaido isn't clear, but it could mean that he may just have to step in and lend a helping hand to Luffy if he really has to.
Up until this point, Caribou has been nothing but antagonistic towards Luffy and his friends. Initially, he and his brother Coribou would make their mark on the pirating world by killing Marines and forming the Caribou Pirates. They would then attempt to join Luffy's crew in an attempt to destroy them from the inside but ended up joining a group simply masquerading as the Straw Hat Pirates instead. It was only after the Marines and the real Luffy exposed the imposters that Caribou realized his mistake.
Their paths would cross once again at Fish-Man Island, where he would attempt to lead a raid against them, but ended up as their prisoner instead. Franky would seal him within a barrel and he eventually ended up in Mermaid Cove, where the mermaids set him free unwittingly. Caribou then began kidnapping mermaids to sell as slaves until a failed attempt at kidnapping Princess Shirahoshi led him to run into the Big Mom Pirates Pekom and Tamago. He was defeated in battle, then began kidnapping mermaids again. This time, however, he was caught by Jimbei.
A series of events led him to finally be captured by X Drive, which is how he ended up in Wano Country, imprisoned at the Prisoner Mine in Udon. It was here that he met up with Luffy and tried to win favor with him. Luffy wasn't having any of it, though.
After being set free by Raizo and helping free Luffy and the other prisoners, Luffy finally accepted his help. He would then go on to help Raizo disable the communications network in Udon, further solidifying his alliance with the Straw Hats. What he's done in the time between then and now in One Piece is mostly unknown, but it appears that he may be gearing up to help Luffy once again, if only to ensure his own survival and escape from Wano.
