Chojusen entered the Marines as a Vice Admiral from the get go, and would have started as an Admiral if it weren't for the restriction of there only being three slots available. Chojusen wasn't stronger than any of the admirals when he entered, so he could only accept the "mere" position of Vice Admiral.
With that status, Chojusen was given a small fleet of marine ships to command and sail through the seas with. There he could relive his pent of teacher's withdraw and teach the more valiant marines he saw about Haki, while he went all over the grandline in conquest to end pirate tyranny!
When he started out as a marine life was all good. He had easier access to the more dangerous locales within the world and could help the world become a better place. But as he stayed in the marine corp for longer, he noticed some rather disturbing undercurrents. These, "law-abiding" marines weren't as clean as Chojusen thought, and the stench of corruption slowly made its nasty presence increasingly aware.
Chojusen was sometimes tasked with missions that called into question his belief and ideals. Kill off an entire island, just because they have information on World Nobles? Protect a snot-nosed inbred failure of a human being that gets satisfaction from the torment and suffering of others? Defend a tyrannical Warlord pirate, just because he's allied with the Marines?
Some of these morally questionable missions were directly dismissed by Chojusen and the marines didn't care too much as they had others more than willing to complete them. They just let Chojusen do as he pleased as he followed the marine's core values of hunting down evil pirates. It was during one of these escapades that Chojusen had interests called into question, when he met a rather ridiculous crew of pirates that, for the most part, destroyed his perception of what a pirate was.
…
One day, as Chojusen was flying through skies as a Chaosfiend Dragon, he actually found some islands in the sky… there he had a blast exploring these ridiculous natural islands and met with a rubber boy. When the two met for the first time, this rubber lunatic actually tried to ride Chojusen in his dragon form… Chojusen almost killed off the idiot treating him like a mount by knocking him off his back and causing him to fall through the clouds and back to the world below.
Chojusen felt bad as he could tell that the rubber boy would either spatter into meat paste from falling from this height or drown due to his Devil Fruit powers. But more importantly, Chojusen could tell that the rubber boy only had the stars of worship in his eyes when he tried to… uh, ride him… So he caught the rubber boy before his inevitable death and glared at him after dropping him off in the ship he had shot himself from to try and ride Chojusen.
Still in his Dragonified form, Chojusen glared at the rubber boy, but only received even greater looks of worship… and it seemed like two more idiots had arrived to donate some precious faith energy. One had a long nose, while other looked like a small raccoon humanoid. Unbefitting of the situation, a grand and majestic Chaosfiend Dragon was treated as a zoo attraction…
As minutes passed, more people left the interior of the ship that was sailing through the sea of clouds and eventually Chojusen got some natural responses. A blonde-haired man and a green-haired swordsmen got into fighting stances when encountering an intimidating Chojusen, while an orange-haired lass coward in fear from him. Then another weirdo with long black hair popped out, who treated Chojusen like he was just a normal everyday occurrence; no biggie, it's just a friggin Dragon…
"Oh my god~ Is that a DRAGON." The long nosed idiot in conjunction with the raccoon kid said at the same time.
"It must be a dragon! But it's a friendly dragon. You guys didn't see but he actually rescued me~" the rubber boy said.
"Hmpf! Whatever it is, we better make sure its not going to kill us!"
"Just this time, I'll agree with the brain-dead swordsman" the blonde-haired man said.
"Guys, don't anger it! Its a dragon. A DRAGON!!!" the orange-haired girl pleaded.
And all the while the blacked haired lass, was the most bold of all the others around, directly coming next to Chojusen and even measuring him…
Rather disgruntled by this band of oddballs, Chojusen backed off a couple steps and reverted back to his normal state. He didn't like constantly having his Vice Admiral clothes on, so no one could tell that they were facing a high level marine.
"Um… Are you guys pirates?" Chojusen asked. He had only now realized that he recalled seeing this rubber boy's picture somewhere on the bounty board in Marine HQ.
"Yes! Would you like to join my crew." The rubber boy didn't even try to hide his desire. 'Are you kidding me? A Dragon in my crew? That would be epic!' thought the rubber boy.
"Uh… You don't seem like the pirate type…" Chojusen said, much to the rather nonchalant response of everyone around him. He could even faintly hear them say something along the lines of "We're just pirates to fulfill our dreams..."
Well, this crew was quite unlike anything Chojusen had seen so far, so he decided to stick around and see what kind of pirates they really were. After showing everyone that he was a person, and not a divine dragon, everyone let him blend in, but it was almost too easy? Like, they barely even cared…
In this little adventure in the sky islands Chojusen started befriending these weirdos rather quickly. The first to get on his good side was the crew's cook, Sanji. This man's cooking was above the level of Grandmasters and into the realm of the Dao… somehow he could add intent to his cooking, which made him and Chojusen instantly become pals. And with the sheer quantity of random recipes Chojusen had accumulated from three planes, he could make rubber tires taste heavenly…
The next person that shared a bonding moment with Chojusen was the green-haired swordsman, Zoro. Chojusen was glad to meet a fellow training fanatic; though it was sad that Zoro was nowhere near his level… But didn't him from sparring with the swordsman!
Next were the Crew's sniper, Ussop, and doctor, Chopper; the long nosed man and the raccoon kid. These two practically fell in love with Chojusen alongside their boss, Luffy, just off the pretense that Chojusen could turn into a dragon. And the two females of the crew? They were like ice and fire; completely opposite in most ways.
Nami, the navigator, didn't like Chojusen at the start and treated him like a threat for the longest time, but Robin, the archaeologist?, didn't mind Chojusen in the slightest and would often talk with him to pass the time.
Chojusen felt oddly at home with these so called pirates, like he was part of a big family, so he travelled with them for a while. They had a rather hectic time in the sky islands, antagonizing a so called god, who was nothing more than an idiot had had been lucky enough to eat the Rumble-Rumble fruit.
This guy, who really would be godlike if he had taken just a small bit of time to train, wasted an amazing devil fruit instead. He had the powers of lightning, which included disintegration, and teleportation, but was so clumsy with the use of his powers that even Luffy managed to defeat him; and he didn't even use Haki to accomplish it…
Even after the Sky Islands, Chojusen decided to stick around Luffy and his crew. They went to Water 7, and Thriller Bark together, but Chojusen didn't help Luffy out too much. He just stuck around as a spectator and watched to gain a new perspective of what a pirate crew could be like. Luffy's crew wasn't just the random group of idiots he initially thought they were.
They truly were like family and in a sense, they might have even been closer. Chojusen also saw how they did things that they felt were good in nature, very much the antithesis of what he had seen in most other pirates. They had their own code of morals and their own trust in each other, which was comparable to the bonds Chojusen had made with his friends and family in the lower planes.
Unfortunately after the trip to Thriller Bark, Chojusen was called back to HQ in preparations for a certain war against the infamous Whitebeard Pirates. He had grow several times more powerful after training through the adventures that Luffy's gang had, and was ready for action. Thus Chojusen bade farewell to his pirate friends and found his fleet of marine ships, before heading back to HQ and get the details of the situation.