The basic idea behind this trick is to take the Hidemasa Hook (created by Japanese 1A player and Duncan Crew member Hidemasa Semba) and turn it sideways. Actually, the real idea that led to this trick was to make a something that looked like a special move from Street Fighter II... but I digress.
What happens, more or less, is that you throw a normal breakaway, and then pop the yo-yo up. While the yo-yo is in the air, you swing your throwhand so that the string whips through the air and hits your freehand finger. When it hits the finger, it'll wrap around it and create a horizontal loop. The idea is to get that loop in the gap of the yo-yo Ã¢â¬â€ no easy task, but a very cool effect if done properly.
So, what's the big deal? It's no revolutionary trick, but it puts a unique spin on the classic hook formula by moving on a completely different plane than usual. And, I mean, you're doing a freakin' sonic boom. Can't touch that.
Step 1: Throw a Breakaway
The first step is to throw a breakaway. It doesn't really matter if you mount a trapeze or just go to a sleeper, but it is important that you throw a breakaway instead of a frontstyle power throw, because the spin of the yo-yo helps "suck" in the string into the gap instead of pushing it out.
I'd probably recommend learning it from a sleeper, 'cause it gives you more time to whip the string around... and more time means you can shout "SONIC BOOM" and get the dramatic motion in, too.
Step 2: Throw a Horizontal Hook.
This is the real body of the trick. In the original Hidemasa hook, you threw the string in the same plane as your yo-yo towards your freehand, letting it wrap around your finger and, more importantly, fall into the yo-yo's gap. In this trick, instead of moving the string upwards parallel to the yo-yo, you're pushing the string perpendicular to the yo-yo in a horizontal motion across your body.
This step isn't actually that difficult, I just like to act mad hard. Basically, pop the yo-yo up and then swing your throwhand forward away from your body so the string lashes out around to the other side of the yo-yo. Make it pretty! I'm not really good enough yet to make the slow, huge loop, but be sure to make it look as sideways as possible.
...and if you're having trouble working the motion, seriously. Watch Guile throw a Sonic Boom in Street Fighter II. It's the same motion.
Step 3: The Hook
This is the hard part. Just like a normal hook, the string hits your finger and a loop forms. That loop goes into the gap of the yo-yo and you have an awesome lil' formation.
Except, this time the loop is a touchy little bitch.
Whatever! You can do it. It's a pain, but once you figure out the spacing you can hit them all the time. I don't think there's really a "secret"; I came up with a bunch of "secrets" to hitting it while I was learning it, but in the end, I think it's just practicing until it clicks.
I let the bottom part of the loop hit around my wrist and the top hit the middle of my finger, 'cause it makes for the biggest loop possible. The downside is that being on the wrist causes the yo-yo to start to tilt quicker, so, uh, dismount fast.
I also think it's easier on taller yo-yos. YWET and Throw Monkey por vida.
Step 4: Stand in Awe
Yeah, you did it. You the man! No, really, you the MAN. That's right. You, dogg. Rock on with your bad self.
Step 5: Dismount
The dismount is pretty simple, and you can probably figure it out yourself, but just in case...
Somersault forward. The yo-yo will be in a bind, so move your throwhand forward along the inside of your body to undo it. You can also just do this trick as a repeater by popping immediately out of the formation and starting the process from step 1, but make sure that you pull all the string out of the gap or it'll snag on you. From there... I dunno! Do whatever. This is kind of a one-shot move, but it looks best at the end of a combo or mixed up with other hooks.
Want to see other hooks? Look up Anti-yo team member Ryosuke Iwasawa for the best laceration tricks on the planet.