WARNING: The following contains spoilers for One Piece Chapter #1015 by Eiichiro Oda, Stephen Paul and Vanessa Satone, available in English now from Viz Media.
While One Piece Chapter #1015 mainly focuses on Momonosuke's escape from Kaido and his inspiring the alliance to keep fighting after Luffy's fall, the chapter ends on one of the most anticipated encounters since the start of the Onigashima Raid. Kaido's own son, Yamato, is finally ready to stand up against the Yonko.
Earlier in the chapter, Kaido believed he had Shinobu and Momonosuke cornered. As he lunges forward though, Shinobu uses her Ripe Ripe Devil Fruit powers to decay the ground beneath and make a quick escape with Momo. This causes Kaido to shatter the wall behind her, bringing him to the outside of the fortress.
When Kaido makes it outside, someone from the rooftop calls out to him: Yamato. Kaido remarks that he should be called "father" by his son, but Yamato completely dismisses that notion, saying he aims to sever those family ties.
While Yamato's only been in the manga for about as long as the Onigashima Raid, he's quickly become a fan-favorite character. Yamato first appears as a masked man who saves Luffy from Ulti. When he takes off his Hannya mask, it's revealed that Yamato is a trans man and that he knew Luffy's brother, Ace. Yamato then gets Luffy to listen long enough to explain himself, saying while he may be Kaido's son, he hates his father for imprisoning him all his life and for trying to carry on the will of his sworn enemy, Kozuki Oden.
Luffy and Yamato share a great scene in Chapter #986 as they're trying to find Momo. To keep him in Onigashima, Kaido shackled Yamato with explosive cuffs that would go off if he ever left the island. Yamato asks Luffy to remove them but doesn't truly believe his father would put a bomb on his only son. Luffy rips them off and they explode, to Yamato's shock. Disgusted by the depths of Kaido's cruelty, Yamato disowns his father. Even despite hating Kaido his whole life, Yamato thought some part of his dad truly loved him, but that hope was shattered when he realized Kaido would rather kill his son than lose control of him.
Since that scene, Yamato has been a full-fledged ally to Luffy's alliance to take down Kaido. While Kaido had primarily been on the rooftop, facing the Akazaya Nine and the five Supernovas, Yamato had been protecting Momonosuke from the Tobiroppo and Beast Pirates. This is what led to his first scuffle with Sasaki before Franky eventually stepped in.
Once Yamato knew he had Shinobu and Momo tucked in the crawlspace away from any danger, he decided to rush off to the rooftop and help Luffy. But, in a stroke of terrible luck, as soon as Yamato left for the roof, Momo and Shinobu were back in danger with Kanjuro and then Kaido. With their locations now swapped, Yamato stands on the roof while Kaido is on the first floor.
It's an understatement to say Yamato had a quick rise to fan-favorite status. After all, he did make it to #11 in the global character poll. And, while it would've been exciting to see Luffy solo the dreaded Yonko, watching Yamato finally get revenge on his father for all those years in captivity will surely be just as exciting.