Ryunosuke

Ryunosuke was a "Rising Dragon" (昇り竜) created by Kurozumi Kanjuro using the power of the Fude Fude no Mi. It was created to aid Kanjuro, Kin'emon, Trafalgar Law, and the Straw Hat Pirates in scaling the leg of Zunesha to reach Zou, and received its name from the Straw Hats.

Appearance
Ryunosuke was a large pink eastern dragon. Due to its poor composition, it had some physical traits which differed notably from actual eastern dragons, namely the head being indistinct from its body like a worm, a fin-like tail, and a pig-like snout; Kanjuro's comrades had initially guessed the drawing as a worm, snake, or lizard before it was brought to life. It possessed scales on its body, and a row of rounded spikes along its back. Its legs were extremely short, impeding its mission to climb.

Personality
Like other drawings brought to life by the Fude Fude no Mi, Ryunosuke was very loyal to the commands of its creator, and thus was determined as possible to complete the task of carrying people up Zunesha that it was given, despite the great strain on its weak form. After completing its journey, Ryunosuke displayed agency of its own as it smiled with joy at its success and the Straw Hats' jubilation.

Straw Hat Pirates
Ryunosuke was created to help the Straw Hats, along with Law and the samurai, get up to Zou. Ryunosuke gave everything it had to do this for them, and they came to recognize its effort, causing them to get a fondness for the dragon and name it. Robin in particular was very attached to Ryunosuke as she thought it was cute. After completing its mission, Ryunosuke smiled at its success before fading away. The Straw Hats were distraught at the loss of Ryunosuke, save for Zoro and Law who viewed Ryunosuke as nothing more than a bad drawing.

Abilities and Powers
Ryunosuke possessed the ability to carry people and climb on Zunesha's skin as it was designed for. Due to being poorly drawn, however, Ryunosuke was rather weak and struggled to just survive, let alone carry people up Zunesha. However, with encouragement from the Straw Hats, Ryunosuke persisted long enough to climb all the way up the elephant, though the exhaustion from this effort caused it to revert back to drawing form immediately following this.

Zou Arc
Ryunosuke was drawn by Kanjuro on the deck of the Thousand Sunny and immediately brought to life with the power of the Fude Fude no Mi. The dragon attached itself to the leg of the massive elephant Zunesha, and Kanjuro, Kin'emon, Trafalgar Law, and the Straw Hat Pirates got on its back for it to take them to the island of Zou atop Zunesha's back. At some point in the climb, the mink Bariete came falling down and knocked Kanjuro and Kin'emon off the dragon's back, and the Straw Hats initially wanted Ryunosuke to climb down to retrieve them. However, upon seeing how exhausted the dragon was, they decided to let it keep climbing. A good deal of time passed, with Ryunosuke continuing to climb despite its distress. Zou back eventually came into view, and the Straw Hats loudly cheered on the dragon to finish the climb, at this point dubbing it Ryunosuke. Ryunosuke finished the climb, and smiled as the Straw Hats celebrated their arrival. It then reverted back to drawing form and lost its consciousness, leaving the Straw Hat group (save for Zoro and Law) in tears.

Manga and Anime Differences
Ryunosuke's climb was extended in the anime; in particular, two filler scenes were added. In the first one, Ryunosuke slipped shortly after starting the climb and slid back down to the Sunny, managing to catch itself before falling in the ocean. Later, right before finishing the climb, Luffy went to sleep and fell off the dragon's back. Luffy then grabbed onto Ryunosuke's horns, causing its forelegs to detach from Zunesha as its body bent back, holding on only by its hindlegs. However, with encouragement from the Straw Hats, Ryunosuke was able to muster enough strength to pull its upper body back to Zunesha's leg.

Trivia

 * "Ryu" means dragon in Japanese.
 * As of now, Ryunosuke is the only character in the series with the same name as their voice actor. Its voice actor, Ryunosuke Yamaguchi, is the son of Usopp's voice actor Kappei Yamaguchi.
 * When Ryunosuke was created, Kin'emon made a displeased remark to Kanjuro, foreshadowing their conflict with Kaidou who possesses the ability to transform into an eastern dragon much like Ryunosuke. Kanjuro responded "an eye for an eye", perhaps indicating that Ryunosuke's help would be a contrast to the strife caused by Kaidou, but given his status as a double agent for the Kurozumi Family, it may have had a different meaning.
 * Ryunosuke has the same suffix in its name as Momonosuke, who can transform into a pink eastern dragon much like it. This theme was indicated when Kanjuro later created animals to climb up to Zou named Nekozaemon and Torasaburo, who share name suffixes with Kin'emon and himself respectively.
 * In the 7th popularity poll, Ryunosuke was ranked 145th.