"So this Ace guy has a brother, and we should be able to find him in the East Blue?" Souffle summarized what has been told to her, "Yep! Monkey D. Luffy!" Yamato confirmed with a nod.
Wait hold on! Yamato!? How!? Well it's best if we show it.
Flashback to 4 Years Ago.
After sailing for a long time and making quite a name for herself despite being a one woman crew, Souffle reached a total bounty of a nine hundred milion, which made traveling a whole lot easier since she was quite intimidating to the marines.
But on these travels she ran into a certain white beared pirated, Edward Newgate, "Gurararara! Linlin is so bad her own children are conspiring against her!!" He laughed after hearing Souffles story, "I just got some inspiration." Souffle downplayed a bit which got a slap on the back From Marco.
"You, are way too humble for a Yonkos child." The pinapple head commented with a smirk, "I have to say, Yamato was pretty chill." Fire Fist Ace commented, "Right, you met Kaidos brat..." Marco remembered, "I'm sorry Yamato?" Souffle repeated in curiosity.
Newgate chuckled a bit, "Never met him, but from what Ace told me, he hates his father as much as you hate your mother!" He informed, still amused at how those two couldn't take care of children if a book about it was thrown at their faces, "I see... And where is this Yamato exactly?" Souffle asked, plotting something.
Sometime After.
Souffle managed to make her way up Wanos borders using her devil fruit to give the ship legs and climb them, and after a while made her way to Onigashima, and the sight of an unknown ship approaching alerted a lot of people so she went into hiding for a bit, during which she ran into none other than the person she was looking for.
"So you're Yamato?" Souffle asked the masked person who nodded in response, "Yes, but... How do you know me?" He questioned in confusion, "I met Ace of the Whitebeard pirates." Souffle explained surprising Yamato, "He joined the Whitebeard pirates!?" He exclaimed in pure surprise.
This confused Souffle a bit, "Wasn't he when you met him?" She asked, "No! The complete opposite! He wanted to kill Whitebeard!" Yamato revealed much to Souffles stupor, "...Funny how it works..." Souffle commented with a hint of a smirk.
With the moment of silence that was brought after that, "Say, you sound awfully feminine for a son." Souffle brought up, "Oh that... Well I'm not exactly male." Yamato informed as he took off his mask revealing to be female, "I'm following in the footsteps of my fathers greatest enemy! Kozuki Oden! And since Oden was a man, I'll be a man too!" Yamato boasted confidently.
"...Yep, I've decided, you're joining my journey!" Souffle said with a smile, "Wait, what?" Yamato said in confusion, "You're the kind of person I like! So come with me!" Souffle insisted, grabbing Yamatos hand and pulling him along, but Yamato put a lot of resistance, "I wish! But I can't!" He refuted though it clearly was out of his wishes, "These shackles I have on will explode if I leave Onigashima, I don't really believe it, but it's better not to risk it." He explained putting a hand on a shackle.
Souffle gave the Shackles a look before getting an idea, "Hold still." She instructed Yamato as she used Haki and snapped the shackles off, shocking Yamato at the sheer strength, but then Souffle covered the shackles in metal and tossed them away to avoid getting caught in the possible explosion, which happened and it blew a hole in the wall.
The sight of the hole made the two freeze for a moment, "What are the chances no one heard that?" Souffle asked with fake hope in her voice, "In this area? Absolutely zero." Yamato replied before turning to run along with Souffle.
"That was incredible though! How do you have such powerfu Haki?" Yamato questioned along the way, "Genetics? I am Big Moms daughter!" Souffle revealed, "The Emperor of the Sea!?" Yamato exclaimed, recognizing the name.
Flashback End.
And that's how Souffle and Yamato met, but it's the past, let us focus on the now!
"So how is Luffy like?" Souffle asked curiously, "Never met him personally, but he did sound fun from what Ace told me." Yamato explained as they kept sailing towards where they intercepted a marine call talking about Luffy.
Thing is, when they got there, they saw one thing, a desert, "This must be Alabasta." Souffle deduced as that's the only desert she knows of, "I don't know if we have enough water." Yamato brought up causing Souffle to groan in frustration, at least until a group of people passed by heading to a goat ship they completely missed somehow.
"Hey wait a moment!" Souffle called out to them, "You wouldn't have happened to see a Monkey D. Luffy back there right?" She asked, to which most of the group seemed unwilling to answer, but then a kid with a straw hat replied, "That's me!" He said causing the orange haired girl to punch him in the head.
The information made Yamato smile, "So you're Aces brother! He told me a lot about you!" He informed while shaking the rookies hand, "Your brother knows such beauties!?" Sanji exclaimed in shock and jealousy, "Hey Yamato is a man you... Twirly eyebrow... Guy?" Souffle attempted to insult and came up blank, "Huh?" The guy with the long nose, girl with orange hair, and twirly guy let out in confusion.
"So anyway I see you got your crew going on, which is too bad since we wanted you to join ours..." Souffle said a bit sadly, "Why don't we join theirs?" Yamato suggested, "Of course!" Souffle exclaimed in realization, "What?" The long nosed guy questioned, "Yeah sure!" Luffy agreed, "Goddammit..." The green haired swordsman said with a facepalm.