Oda

"We know who you are, kid! If I beat you, then I can just beat off any Yakuza right?"

- Some stupid Yankee

He finished middleschool and entered school with ease, but it didn't stop anyone from acknowledging Oda once again. And his experiences in school would progressively became worse - especially with the students. Upper-grade students often had problems with Oda's existences and especially the stronger appearing ones would only pick fights with him. Thankfully, his father's plan of making him the next wakagashira instantly turned the tables on them and he'd immediately fight them off with ease.

But with the constant fighting only hindered his capability of attending classes and he was prone into getting into trouble and likely the police would be involved if anything happened... that involved him. In the end, he was able to graduate and he barely finished his college years before leaving education entirely to take over his father and late-brother's position.

"There was someone, like you, who fought the world to keep the Yamatando clan alive. But it's funny... because he is now the very man who is fighting to do the complete opposite. As long as he is alive - we will constantly falter until we fall." 

- Current Chairman of the Yamatando-kai

Oda watched his clan dwindle down to small numbers, since he was a small child. And he knew how important the Yamatando was to his family and he was raised to think the same way. And everyone around him and his clan only were on the constant prowl and took opportunities to try and wipe the Yamatando out from existence.

Mogamachi had no plans to letting the clan fall. Oda often went through great lengths when it came to fighting and the amount of bodies he's beaten were unrivaled. Everyone potentially recognized Mogamachi's abilities and it was only attracting more and more attention for him and the Yamatando - both good and bad.
Because of his successes brought in several small, yet passionate people, who wanted to follow Oda's footsteps. Hence joining the Yamatando-kai, despite it's once-dwindling numbers, there were people joining it, because they wished to be in the presence of the legendary Oda.
The current chairman of the Yamatando-kai surely recognizes Oda's constant successes and wins in the name of the clan. Eventually the chairman shares the secret and the reason why the clan almost fell - which remained a secret for all of the chairmen: a once legendary general that went by Akuma - a living demon who left the Yamatando-kai, hides himself from the world, and secretly takes any opportunity to pick away everything the clan has. The chairman himself is at awe as to why Akuma hasn't finished the clan off.

Oda, who now knows of the reason why, spends years trying to learn and pinpoint Akuma. However, the countless years of trying to figure out his whereabouts only sacrificed the several members of his own family. And every death affected Oda greatly, hoping that he'll come close enough to be able to kill Akuma.

• Mogamachi was pretty much born into the Yakuza. Was supposed to be in law that works for the clan, but plans changed after his older brother's death. He begins working to become one of the clan's generals.
• Mogamachi's connection with the Yakuza made it rather hard to get through school. When he barely finished college, he stopped it completely to be with the clan.
• Fought and defended the Yamatando for years and became the most important figure in the clan. It was solely because of him that people began to join his family. If they couldn't join the Oda family, then they still joined the clan nonetheless.
• The chairman gives him the reason why the clan remains weak. Hence Oda spends the rest of his life trying to find Akuma, the legendary demon who is constantly trying to remove the clan.