Ichiro is the oldest brother from the Three Criminal Brothers. He is very good at bluffing and lying over various objects which he sells to get money. Overall, he is good at acting and knows a lot of techniques that persuade people to try his products.
Ichiro appeared after the Varia Arc. He and his brothers decided to steal from the Sawada family. When both of his brothers failed, he decided to go by himself to the Sawada house and sell them school supplies. When he arrived, he came across Tsuna. He told him that his products would raise his school grades in no time. He also told him that he had made a deal with his father (he had already asked and knew that Iemitsu was away). Tsuna brought him inside even though he was sure he didn't want to buy his product. While siting at the kitchen, Bianchi gave to Ichiro a poisonous drink. He drank it and ran to the bathroom. Then, Lambo chased I-Pin into the bathroom and accidentally used the Ten Year Bazooka. Future I-Pin appeared and stepped on Ichiro, who had fallen down. Like always she said she was worrying about not delivering her noodles to Kawahira in time and run away. Then, Lambo, in a celebratory mood and holding maracas, forced Ichiro to dance with him. Ichiro was slowly going crazy with all that stuff when Gokudera, Ryohei and Yamamoto appeared. He thought it was a good chance to sell them products too, even though they rejected him straight away. Trying to persuade them, Ichiro defied home tutors. When Reborn heard that, he hit the floor with Leon in the hammer form, creating a hole. Ichiro was so scared he tried to run, but he slept from Bianchi's python, who was lying down. Then, Fuuta started ranking and Ichiro started floating. When it ended Ichiro, ran but fell on Gokudera, who dropped a few dynamites. When Ichiro saw them, he ran away. After a while, Tsuna found out their real purpose and chased them with his Dying Will to the police.
- His name shows that he is the eldest son, as "ichi" means "one" in Japanese.