The nunchaku is constructed of two short sticks connected by a rope or chain. Though it’s origin has been lost to history, with no definitive lineage known (even the word itself isn’t quite established, with the most common theory suggesting it derives from the Chinese characters for the chang xiao ben – a two-section staff – after adopted into the Japanese Ryukyuan language), the nunchaku is most commonly thought to be a flail for threshing rice or soybeans in Southeast Asia. However, other ideas include a horse bit or a hyoshiki, a wooden clapper carried during night watch.
The nunchaku was incorporated into martial arts in Okinawa, and from there migrated to the rest of Japan. The most common practices using the weapon are kobudo, karate, eskrima (from the Philippines), and hapkido (Korea). In most disciplines, the nunchaku is the first weapon given to students, teaching self-restraint, discipline, and posture for more advanced weaponry. Additionally, beginning with this increases hand speed and conditioning.
While it is an excellent weapon for a disciplined martial artist, the nunchaku is not found in the traditional 18 disciplines of ninjutsu. However, there is a chain weapon that practice with the nunchaku can help master. The kusarigama is a wooden handle with a perpendicular curved blade at one end and a weighted chain at the other. The chain can be thrown as a distraction from long range while the wielder moves in to strike with the blade. Practice of the kusarigama (or kusarigamajutsu) has been incorporated into ninjutsu, and proficiency is required of anyone seeking to be a ninja master.
Michelangelo and nunchaku are almost as well known as Raphael and the sai. Like his brother, Mikey’s weapon of choice is not a standard of ninjutsu. However, this isn’t as important a point as it is for Raph. As the youngest brother (and likely least trained ninja), Michelangelo shouldn’t have the same proficiency with weapons that his brothers do. So it makes sense that he would have an implement designed for beginners to teach certain basic skills. So even though it’s not a standard instrument, it still makes perfect sense for Michelangelo.
The nunchaku also fits with Mikey’s personality. Despite how funny, upbeat, and happy-go-lucky Michelangelo is, he is also very young and underdeveloped. That means that he doesn’t have the same kind of self-restraint as Leonardo, or the focus of Donatello. As such, trusting him to carry around a bladed weapon is a bit premature. Instead, he gets an instrument that can cause damage without seriously hurting himself or others, allowing him the proper time to mature and grow.
Unlike Raphael’s situation with the sai, using the nunchaku is actually preparing Michelangelo for ninjutsu weapons. In fact, the kusarigama has already been incorporated into his nunchaku in the most recent incarnation. This shows that despite still being at a lower level of mastery, Mikey is learning what he needs to, and is at a point where adopting one of the traditional weapons of ninjutsu is okay if handled correctly.
Mastering the nunchaku gives Michelangelo the opportunity to focus more of his energy on other disciplines of ninjutsu 
instead. If his weapon training is kept to minimum, then he has no choice but to practice stealth techniques, hand-to-hand combat, and the other aspects of the craft. That means by the time he’s ready for strictly bladed weapons he’s already adept at several other disciplines, meaning that he can exert that much more energy on the weapon training while simply keeping the other areas refined. This shows through in the 2012 series, when he proves to be exceptionally skilled at stealth with water balloons and egg smoke bombs.
While he may be young, Mikey is far from unskilled. However, his weapon is meant for a beginner and not a part of traditional ninjutsu, which shows that he has a long way left to go. But as his other skills develop, so will his proficiency with weapons. His upbeat attitude will keep him at the top of his game, and allow him to practice hard even in the worst of times, until the day he achieves the title of ninja master.
