9B (pronounced kyuu-bi) is a smasher from Osaka, Japan, who mains the Ice Climbers in Brawl and Bayonetta in Smash 4. He is considered to be the best Brawl Ice Climbers in the world as well as the top Brawl Lucario player in Japan, and the best Smash 4 Bayonetta player in Japan. He was also formerly a notable Shulk, Ryu, and Mewtwo player, but has since dropped the characters. Due to his infrequent tournament losses, 9B is currently considered to be Japan's top Brawl player along with Edge, and was ranked 1st on the 2014 SSBB Player Rankings (tied with Nairo). He is currently ranked 8th on the JAPAN Power Rankings and was formerly ranked 17th on the Panda Global Rankings.
9B is said to have created the faster yet more difficult chaingrab for the Ice Climbers in Brawl. This involves using Popo's down throw to start the chain, having Nana re-grab, then executing a back throw so Popo can regrab.  The following description is from the Youtube video showcasing this technique, which can be found at the bottom of this page or by clicking the reference tag before this sentence. It explains how the technique works and why it is a faster chaingrab.
When you grab with Popo, naturally, Nana will grab as well. Since Popo normally grabs the opponent, Nana will be left with a dead grab animation. An experienced player in the Ice Climbers match-up knows this is the PERFECT time to MASH THE HELL OUT OF THAT CONTROLLER, as the Nana cannot re-grab just yet. Since Popo's B-Throw executes in so few frames, Nana will have to wait to finish said animation. HOWEVER, D-Throw's animation lasts significantly longer, giving Nana time to finish her grab animation DURING the throw, meaning the opponent can't mash out. After D-Throwing with Nana, Popo doesn't have a grab animation, so you can instantly throw again; buffered B-Throw being your fastest option. That's how this chain came to be.
The main mechanics of achieving this string includes buffering a walk in the opposite direction after re-grabbing with Nana. The B-throw will then come out accompanied by a turnaround by Popo, not a walk. This allows Popo to re-grab the opponent and thus continue the chain.