Master Na is a good instructor, but his purpose in martial arts is not to teach his students to their full potential, but to suck out as much capital as he possibly can from their bank accounts. even with all his experiences and vast amounts knowledge, he's rather position himself as a businessman than anything. he charges too much for lessons and he gives out FAKE black belts. YES, I SAID FAKE! i would know, i have one. Instead of a world-recognized certified issued from KUKKIWON, he prints out the certificates himself in his home office under the organization called "ITMA" aka International Masters Associations. How do i know? I know because shortly after I received my from Master Na, My parents and I moved to another state and when i tried to enroll in another school and showed them my certificate, they said it was worthless. ABSOLUTLY WORTHLESS! After investing nearly 4000 dollars in tuition, seminars, and testing fees, all we got in return was a sheet of paper that i could have made myself, saying that I'm a "certified". Unfortunately, no one else in the entire face of the planet thinks I'm "certified." The deep respect i had for Master Na is now completely destroyed. I was extremely disappointed. It is like being conned by your hero/mentor.