Sawada Tsunayoshi, or Tsuna, is a cabin boy aboard the Fiertia.
There is a reason that Tsuna has the nickname "No Good Tsuna"-- he is absolutely terrible at everything he does. He isn't intellectual nor is he athletic. His coordination is way off and he possesses absolutely no special skills at all. He is constantly tripping, breaking or dropping things. In other words, he's useless.
Despite this, he is extremely optimistic. He prefers to (or at least tries to) look on the bright side of things and he is constantly smiling. He loves helping others, even if he doesn't get anything in return. The feeling of accomplishment is enough for him. His attitude towards others is the complete opposite to what he thinks of himself. While he has no belief in himself, his belief in others is endless. He is extremely supportive and loyal to his friends. Described as compassionate and kind, he is the type of person that will stand by your side no matter what.
Tsuna's self-esteem is quite low and he himself acknowledges his worthlessness. He is also quite naive and very easily bullied. It doesn't take much to trick him and he doesn't know when he's being taken advantage of. Disliking confrontations, he would usually try to avoid them by agreeing even if he disagrees in his mind. He hates antagonizing other people. Quite meek in personality, he would usually start stammering if he gets nervous, which happens often. He is very hard working though and puts his all into everything he does.
Tsuna grew up in Solare, raised solely by his mother. His father was rarely around for his childhood even though he made an effort to be in Tsuna's life as much as possible. Growing up he was content with what he had and didn't mind that there were many things he lacked. He thought things were just fine as they were until one day when men from the well-known and respected family of Vongola showed up at his home announcing that he was to be their tenth head. Through some blessing (or was it a curse?) Tsuna was the last remaining blood relative of the ninth Vongola by way of an illegitimate family that belonged to the first.
Immediately he was removed from his comforting home and swept across the country to Bellcius where he was forced to become someone he was not. He took countless lessons on etiquette, fencing, music and literature, all of which would assimilate him to the lifestyle of the nobles he was now a part of. But he was completely miserable. He didn't fit in at all. At social gatherings he would stand at the side, pretending he didn't exist. At 'home' he was emprisoned within an empty house, forbidden to go outside, lest some danger befall upon the precious Tenth. People around him treated him as if he was something fragile that was on the verge of breaking. Even those who were close to him treated him differently. The days turned to months and the months turned to years as Tsuna grew more and more alone, trapped in what seemed to him a prison.
One night when the Fiertia was docked at Bellcius, Tsuna sneaked out of the mansion and stow away on the ship hoping it could bring him back to his real home. He knew it was cowardly to run away, but Tsuna was a simple person and what he was thrust into intimidated him. It was the complete opposite of what he wanted. Once on board, Tsuna was quickly taken by Yuri's philosophy-- he admired the captain's resolve to help people. So putting aside his plan of returning home to Solare, Tsuna decided to stay with the Brave Vesperia and do what he can to help Yuri, no matter how little his contribution was.
So his life on board the ship was born. He was given the simple job of being a cabin boy, and while his work was less than perfect he was happy. It was never dull on board the Fiertia, there were friends he could talk and laugh with, there were no false formalities and least of all, he could help people.