With this Super Move, Koichi is able to turn the repulsion force emitted from his limbs into a suction or adhesive force; allowing him to stay strongly attached on any surface, even though this is the one of a moving bullet train. To make this thing work, Koichi must alters the direction of the force of his Quirk.
He discovered this requirement by accident, when he jumped on a moving train, but apparently it's something he's been doing subconsciously. When he felt his body was lifting off during the turns or against a headwind, he simply repressed it.
It is not necessary for Koichi to use all his limbs for this new movement, he can use only his feet to cling himself on a surface thus leaving his hands free to attack.