45ers refers to those earning 45,000 perica per month instead of the usual 92,000 perica.
Tobaku Hakairoku Kaiji
When Kaiji discovers that Ōtsuki is cheating by looking at the results of his wins in the notes of Miyoshi, he decides to gather up the losers within the room of Group E and plan out a strategy to take down Ōtsuki. Mainly being that he needed enough perica to make any significant damage and he needed more people to gather perica faster. He does not reveal to him his plans to beat Ōtsuki but instead convinces them on his own judgement when the time comes.
After Kaiji defeats Ōtsuki, he uses his day pass to gamble again to earn enough money to pay the debts of all the members of the 45ers. This gamble, being the Bog.
The 45ers are given the opportunity to witness Kaijis gamble with the Bog via live feed provided by Hyōdō who wanted to break down the spirit of all those who are watching in the underground labor camp by witnessing Kaiji's defeat by the pachinko machine.
However, Kaiji manages to beat the Bog instead (much to Hyōdōs disappointment) and barely earns enough money to pay off the debts of the 45ers and free them from the underground labor camp (including Hiromitsu). After meeting up and spending their time together, they eventually go their separate ways.
Tobaku Datenroku Kaiji
Tobaku Datenroku Kaiji: One Poker Hen
Miyoshi and Maeda play a small cameo in the beginning of the arc, accompanying the desperate Muraoka.