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 Maruken, Bulldog has some kinda mysterious power to draw people towards him .
While according to Bulldog'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.
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.
One day, Bulldog was going to declare himself to a girl when he saw Harumichi Bouya following her . He was very nervous but after talking to Bouya he got at ease as they both thought she looked like an angel . After getting rejected by her, Bouya started crying for Bulldog saying he knew that feeling, they later became brothers and best friends after that .
As they were introducing themselves, Bulldog got a challenge by Maruken and Kakuken from Kurosaki Industrial, his rival school . As his usual partner wasn't around, Bouya offered himself to help . Bouya knocked out Kakuken in one hit, letting Bulldog and Maruken stunned . They didn't know his identity and were shocked to discover he was Harumichi Bouya, the top dog of Suzuran .
After the fight, Bulldog called Maruken and Kakuken for a meeting, he said that they blindly fighting each other and didn't see how many strong guys were growing around them, but if they joined forces they would be a match even to Suzuran . And so the Kurotaki Alliance was born.
Their first target would be the Extreme Dragon Syndicate, formed by a Takiya drop out . Bulldog wanted Bouya to help them but after a misunderstanding with Maruken and Kakuken they all had a fight and the alliance broke out .
Bulldog decided to take the Extreme Dragon Syndicate by himself , without knowing it was all a plan from Hiromi Kirishima with students from Kurosaki and Takiya to fool their bosses so they all will join forces in the last minute, reforming the alliance once again and destroying the Syndicate .
The Kurotaki later was challenged by an alliance made by the leader from Tsukamoto High, Yagisawa Akira, and the leader from Nanamori Industrial, Hirajima Shingo. They wanted a one-on-one fight and the loser would have to join under the winner. Bulldog fought against Ishii Tsuyoshi and won . After the fight, not only Tsukamoto and Nanamori join, but Kawada 2nd High and Yurikawa South join as well.
Recognized as the strongest fighter to ever run Takiya Commerce, 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.
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, Bulldog decided to join his father's company Furukawa Ironworks.
Five years later, he took over the reins when his father retired, and with his great physical strength and his natural cheerfulness, the company prospered.
- Bulldog vs. Pon - Won 
- Bulldog vs. Nakano - Won 
- Bulldog vs. Yamamoto - Won 
- Bulldog vs. Ishii Tsuyoshi - Won 
- Bulldog vs. King Joe - Won