The Yuuki Slack is a trick that involves a slack.
Steps[]
So you begin a side style throw, and start in a trapeze. You then pinch your index finger and your thumb of your non throw hand. Flack the string by rotating it with a clockwise motion and cast the string sigment in a double or nothing, even dismounting from that double or nothing off to the side. Hit the yo-yo on the bottom of the string and slack the yo-yo in the opposite direction. You catch a string segment as it's going around and then you repeat the motion again. So you dismount, you hop onto the string under trapeze and then you slack it over into a double or nothing back and forth, back and forth. After you've done your fair share of Yuuki Slacks, you dismount and you bring yo-yo back up.