Full summary, thanks to redon from Arlong Park Forums.
Chapter 1,026: “Crucial Time" (“天王山” in japanese, it means too “watershed”).
In the cover, Nami and Leo are making a t-shirt for a lion cub who is next to his father (they are Minks). All of them are in a store called “Haute Couture Nami” and the t-shirt design is the lion-sunflower that Bell-mère made for Nami when she was a child (in the clothes she inherited from Nojiko).
Chapter starts in the “Flower Capital”, there people are enjoying the festival. Tenguyama asks Toko if she is having a good time, she says yes while she eats a candy. We see a little flashback of the moment when Tama leaves Wanokuni with Speed in a boat towards Onigashima. Tama tells Tenguyama that she has to go help, although she doesn't know if she will return. Speed says she will protect Tama. Back to the present, Tenguyama wonders if Tama is safe.
The sky in the “Flower Capital” is covered by clouds, so the people at the festival can't see that Onigashima is approaching to the capital.
Cut to Onigashima's rooftop, we see a Mary (a man from Kaidou's army) that is observing the battle and reporting the situation to the rest of his companions. His voice is amplified to be heard throughout the castle.
Mary: "Report about the mysterious dragon!!
Right now on the roof is the wounded young Yamato.
And in the sky there is something incredible... two dragons face to face!!
The blue dragon is Kaidou-sama!!
And pirate “Straw Hat Luffy” is riding a pink dragon!!!"
Yamato looks at Momonosuke as he remembers some words Momonosuke said to him when he was still a child.
Momonosuke: "If only I could turn into a monster like him...
it would be such a help to everyone!!"
The Mary keeps talking, saying that the identity of the pink dragon is unknown but there is no doubt that it is an enemy. We see Queen surprised at the Mary's report.
Queen: "Was Yamato the one who stopped Kaidou-san?"
Back to the battle between dragons. Kaidou opens his mouth and prepares to shoot his “Bolo Breath”. Luffy tells Momonosuke to shoot something from his mouth too but Momonosuke has no idea how to do it. Kaidou finally shoots his “Bolo Breath” and Momonosuke barely manages to dodge it.
Luffy says something to Momonosuke that shocks him (we don't know what) and then jumps towards Kaidou. Luffy blows up his left arm and attacks Kaidou with his “Gomu Gomu no Elephant Gun” hitting Kaidou's head (that crashes into the ground). Momonosuke thinks about what Luffy told him.
Luffy: "Hey Momo!!
Bite Kaidou!!"
Momonosuke: "I can't, I can't...!!
I...!!"
Momonosuke remembers Kaidou's assault at Kuri's castle after Oden's death and how Kaidou attacked his mother. That's when Momonosuke musters up enough courage and gives a strong bite at Kaidou's body.
Kaidou: "Uwaaaa!!!"
Kaidou screams in pain, Momonosuke remembers the moment when Kaidou told him that his father was a fool of a lord and bites him harder. However, Kaidou turns around and looks very annoyed at him.
Kaidou: "What do you think you are doing!!!"
Although Momonosuke looks at him with fear, he doesn't stop biting Kaidou.
Momonosuke: "You have destroyed Wanokuni!!
I have to stop you anyway.
My father was...!!
My mother was...!!"
Seeing the situation, Yamato runs off to help Momonosuke. But Luffy arrives first and punches Kaidou in the face.
Luffy: "Well done Momo~~~!!!"
Cut to the treasure room on the 2nd floor. The sky is covered with clouds, so Inuarashi has returned to his normal form and is exhausted.
Jack: "The dragon's called the “thundercloud”...!!
The moon has stopped shining tonight.
Huh... Huh...
... If you had attacked me 1 more time
I wouldn't be able to stand again!!"
Inuarashi: "..."
Nekomamushi is in the same situation as Inuarashi, he has almost no strength. Perospero talks to him while holds a huge candy axe.
Perospero: "Don't you blame the moon...!?
You are out of luck!! Perorin ♪"
Nekomamushi: "..."
Perospero: "My luck is too strong for you, cat boss!!"
Carrot and Wanda watch helplessly.
Carrot: "Master Nekomamushi!!
The “Sulong” has disappeared."
Luffy's voice is heard throughout the castle.
Luffy: "Momo!!"
Samuari: "Uh!? Momonosuke-sama!?"
Luffy: "What you have just bitten is one of the “Yonkou” himself!!
Is there anything in this world that you still need to fear!!?"
Momonosuke: "...!!
No..."
Yamato: "..."
Momonosuke: "No!!!"
Luffy: "Go!! You can fly!!"
Momonosuke: "Yes!!"
Luffy: "Stop Onigashima!!"
We can see Zoro and Sanji fighting back to back while they discover the dragon was Momonosuke.
Luffy: "Leave Kaidou to me!!
I will definitely win!!!"
We have now a magnificent double page. In the right part we see a defiant Luffy and Kaidou in dragon form (he's very serious). In the center we see the joy of the samurai alliance at Luffy's words and the news about Momonosuke. We also see the reactions of some characters like Tama, Nami or Franky.
Big Mom: "Ma~~~mamamama!!
Did you hear it!? What a funny guy!!"
Kid: "Of course you have to!"
Law: "What on earth has he been doing?"
Kaidou transforms into his hybrid form and goes after Luffy.
Kaidou: "...
Do you think there still a possibility that you can beat me!?"
Luffy: "As long as I'm alive
the possibility is limitless!!"
Kaidou attacks with his kanabo and Luffy with his fist, both use Color of the Supreme King Haki. There is a massive shockwave of black lightning, but their attacks do not touch (the same that happened with Roger and Shirohige). The impact is so powerful that the clouds begin to separate and the sky splits in two.
The Mary that was observing the battle reports what happened to the entire castle before being knocked out by the Haki. After this, the sky is open and the full moon can be seen clearly again. Jack and Perospero look at the moon in amazement as Inuarashi and Nekomamushi transform into Sulong...
Inuarashi: "What were you saying...!?"
Nekomamushi: "Where is your luck now...?"
Inuarashi and Nekomamushi: "“Oden Ittoryu ”(Oden's One Sword Style)"
Nekomamushi: "“Nikoneko Bam” (Smiling Cat Strike - 猫笑衝突 (ネコニコバーン))"
Inuarashi: "“Inu-spire” (Dog Powerful Cutting Arrow - 犬斬威矢 (イヌスパ イヤー))"
Nekomamushi throws a powerful swipe at Perospero, shattering part of his hat and breaking his candy arm. Inuarashi attacks with his sword-leg like a spear, breaking Jack's belt and piercing his stomach.
Perospero, the eldest child of the Big Mom Pirates, has been defeated. “Jack the Drought”, the All-Star of the Beast Pirates, has been defeated.
A small door opens into the building near where Jack and Inuarashi were fighting. It's Orochi, who has been watching the entire battle in the shadows...
Orochi: "Jack is defeated!?
It has nothing to do with me tho...!!"
End of the chapter, no break next week.