Onizuka's best friend. The two have looked out for each other since their rebellious biker days. After they grew up, the two took on somewhat different paths. Whereas Onizuka floundered somewhat, Ryuji enrolled in technical school and became certified as a mechanic. He worked up from there, to the point that he's now manager of a bike shop.
Still, like before, Ryuji looks out for Onizuka. He was the one who gave him the applications for the private schools (including Holy Forest Academy) after Onizuka missed the public school certification exams. He also passed word from Fuyutsuki about the second chance Onizuka had to apply for Holy Forest.
To this day, he continues to root for Onizuka's effort in becoming a great teacher, strange though it seems for the former bike gangster. But hey, if he wants to do it, why stop him?
Ryuji Danma was Onizuka's partner in their old biker gang days. But Ryuji went to school and got a real job before Oni did, and also got a girlfriend first too. He usually bails Onizuka out of trouble, or drags him around a bit to give him some advice after Oni goes out on another sake run.
At times he's usually the one telling Onizuka "I told you so", and if you know Onizuka you should know why he says that. Even though it seems like he doesn't want anything to do with his old friend, he usually helps him in tight spots and has to pay Onizuka's tab.