Osamu Furukawa AKA Bulldog was the President of The Kurotaki Alliance and a student from Takiya Commerce High School. One of The Four Kings in his generation who are known as the strongest fighters in town. Bulldog became Harumichi Bouya's blood brother through learning about each others inability to get any where with girls. Over the course of the series they develop a strong bond of friendship.
Osamu was well known for being a very charismatic leader, uniting multiple schools under Kurotaki's banner with just his personality alone. According to Bull's successor Nakajima, there's something he can't explain about Osamu that makes him believe by the time he actually witnesses how strong his boss really is, he will have lost to him already, choosing to never challenge Bulldog and was seemingly overwhelmed by his presence upon first meeting him.
Recognized as the strongest fighter to ever run Takiya Commerce High, delinquents throughout Toarushi respect Bulldog's strength, especially Bouya, who on occasion has said if Bull ever got serious, he kinda gets the feeling even he wouldn't beat him. Being a humble person in nature Bulldog has admitted that people had it wrong when they grouped the Four Kings together as the strongest men in town, when in truth even Ryuushin and Bitou knew that the strongest man in Toarushi was Harumichi Bouya.
On top of his strength Osamu is an extremely tough individual evidenced by obtaining victory in all of his fights even when it seemed like he was on the brink of defeat, this often includes enduring many blows from his opponents. His greatest feat of endurance however is when he survived being hit by a semi-truck during his second year. Unfortunately Bulldog would lose the ability to hear in his left ear as a result of this incident.
After graduating high school Bulldog decides to take over his father's company Furukawa Ironworks.