He is the main protagonist of the anime and web manga series. He is in Nanba Prison on larceny charges. He is a skilled escape artist, that specializes in locks.
While his background has not been fully explored, it is shown in a flashback that as a baby he was born in a prison and he even states he feels most at home in prisons. He is also stated to have been arrested for larceny charges, but escaped the same day and has been arrested and escaped prisons the most out of his friends and is described by Hajime Sugoroku as the type of person who deserves to be in Nanba Prison in contrast to his friends, whom he describes as simple minded idiots. In addition, Jyugo mentions that he is a lifelong prisoner. He seems to have met each of his friends independently in different prisons, and it is him who brings them all together when they end up running into each other in Las Vegas.
In the past while in a prison, someone placed shackles on him that no one, not even himself, could remove. He only remembers that it was a prison guard with a scar on the back of his neck and has been searching every prison in the world to find him so he can get him to remove the shackles that prevent him from obtaining freedom. At some point, he was roomed with a violent cellmate whose eyes he ripped out. The main reason he keeps trying to escape prison is to purposely extend his sentence, so he can stay at Nanba Prison as long as possible, for it is the only prison he hasn't checked yet for the scarred prison guard.