Toramaru is a large biker gang led by Chikage Rokujou that is primarily based in Saitama. They act as antagonists in volumes 4-6 of the light novel series, but have since taken on a more passive stance in the story due to Chikage and Kyouhei's newfound friendship.
Not much is known about Toramaru's history before the start of the series. All things considered, they appear to be one of the more charismatic biker gangs within their area. Although there are a few hotheads in their group, they generally don't start too much trouble beyond the usual noise complaint unless provoked. Toramaru's members have their own personal code morals, being against certain iniquitous behavior, such as how they would refuse to harm children and, under Chikage's orders, are not allowed to harm women.
A few members, bored and looking to make a quick buck, find Yodogiri's one million yen bounty on Celty and decide to go for it against the orders of Rokujou. They split up and start combing the city for Celty, and one group comes across Mairu and Kururi, who are also looking for her. The twins passively insult them, which causes them to attack. However, they are thwarted by the timely intervention of Kyouhei and his crew. The Toramaru members gives chase to Kyouhei and the others across the city, occasionally attempting to attack the van with whatever they happened to be carrying at the time, mostly crowbars and pipes.
Meanwhile, the other half of the group managed to track down Celty and started chasing her across the city as well. The groups eventually reunite and attempt to drive Celty and Kyouhei's group into a corner. Kinnosuke Kuzuhara and several other members of the traffic police intervene but only manage to take out a fraction of the group.
Toramaru eventually corners Celty and the others but, as they close in, Ruri Hijiribe appears behind them and attacks. Egor also appears, bursting out of a sack that Celty had been carrying the entire chase, and joins the fray. Egor and Ruri defeat the Toramaru members and force them to retreat. Bruised and humiliated, a few members afterward attempt to beat up Shizuo to vent but only end up getting sent to the hospital.
At some point between volumes, several Toramaru members, along with various friends and family members who are not in the gang, are attacked by remnants of the Blue Squares led by Aoba Kuronuma posing as a member of the Dollars. Many of them were injured and hospitalized and in retaliation, Chikage and several others come to Ikebukuro looking for payback.
For the most part, the gang itself stayed on standby while Chikage did most of the legwork, eventually singling out Kyouhei as the Dollar's "Leader" and challenging him to a one-on-one match. While the two of them fought, a few rogue Dollars members attempt to use one of Chikage's girlfriend, Non, along with a few of her friends, including Rio Kamichika, as hostages to get him to back down. The tactic fails as Kyouhei's friends, along with several Dollars members who were against using hostages, intervene and save the girls. Chikage calls in the rest of his gang and the fight escalates into a full on brawl between the kidnappers vs the Toramaru/Dollars alliance. The battle gets even more chaotic as Vorona, Anri, and even Shizuo arrive for various reasons. Eventually, the kidnappers are dealt with and Chikage orders everyone back to Saitama.