Daizen Tsutomu AKA Tetsuwan Tsutomu is currently a senior student at Suzuran All-Boys High School. He got his nickname due to his strong arm, much like cartoon character Tetsuwan Atom. He lives up to this nickname through his signature move, the Bakudan Punch. A former lieutenant of the Hana-Gumi, after his Boss Tsukishima Hana and the undefeated Hanaki Guriko graduate from Suzuran, Tsutomu is said to be without a doubt the school's strongest man. He also inherited Harumichi Bouya's Bullshit belt buckle from Hana. Making him the fifth and current owner.
Back in his middle school years, Tetsuwan had already built a fearsome reputation and maintained it by holding an undefeated track record. His strength was so widely recognized, that by the time he entered Suzuran, only one person (his enemy-turned-ally, Nakamura Ginji) dared to fight him in his generation's First Year War. When he was a freshmen, Tetsuwan already challenged both of Suzuran's strongest men (Hanaki Guriko and Tsukishima Hana) to separate fights, but lost both fights, which put an end to his winning streak. His losses to the two made Tetsuwan Suzuran's third strongest man - a position he shared with Suzuran grad, Sakota Takefumi. He also swore loyalty to the Hana-Gumi after his loss to Hana. He shares a rivalry with Tsukimoto Mitsunori from Housen which dates back to their middle school days. The two fought so much, that they each gave the other their scars after falling through a glass window while fighting in a mall.
Despite his lack of fashion sense, Tetsuwan takes insults to his looks very seriously and is easily provoked by them. Most of the insults come from his friend and nemesis, Sawaguchi Masaru (a.k.a. Pudding). Tetsuwan and Pudding have a love-hate relationship, with the latter always provoking the former - which always results to Tetsuwan beating up Pudding later. But even if they are at each other's throats all the time, they are still each other's confidants and strongest allies.
Tetsuwan also commands his own faction that originally served under the Hana-Gumi, which includes Pudding, Ginji, Akaike Yuuji, and Aoyama Kouji. As a member of the Hana-Gumi, Tetsuwan has had his share of fights, the most notable of which is his one-on-one victory against Kagawa Kazuya (a.k.a. Gaga) of the Amachi Army. He also took part in the war against The Manji Empire. During Manji's assault on Suzuran , Tsutomu fought and defeated the Enomoto Group's leader, Hama Toshio.
During his Senior year, Tsutomu along with Akaji and Aoji observe the final fight of the incoming generation's First Year War from Suzuran's rooftop. Tsutomu is seen smirking as Aoji notes that Suzuran's reputation must have spread overseas because of the foreigner Tyrone's presence at their school.