That guy there is not Ryo Yabe, he is Takashi Otsuka.
The trick is variation monorail and after that he changes direction of the movement. So it´s done like this: you catch the diabolo sothat your string is in same position as if you were doing over arm orbit. When you catch the D you swing it around your arm so that you have the string aroud your arm, swing diabolo back and change the string side and swing it back.