Who is this mystery Seito guy you fellas are speaking of? I bet he was on point quite a bit if you're searching for evidence that what he said, and trained in, was so much BS like the rampant BS karate that most train in.
Mr. Coffman was a senior American student of Soken. He studied his karate for a few years. He originally trained with Kise Fusei, and then was introduced to Hohan Soken after getting his black belt in Shorinji Ryu. His kata are a combination of Shorinji Ryu and Matsumura Seito. His stances and techniques are often more Shorinji Ryu than Pure Orthodox Matsumura.
Other students of Matsumura Seito, like Nishihira, Gringras and Lindsey continued refining their Seito for decades. Coffman teaches the karate he learned while on Okinawa in a few years of training. Gringras includes the Shorinji ryu kata in his teachings as do his students. For Ron Lindsey they are "extra", but not required for promotion. Nishihira and Akamine both taught very true versions of Seito as Soken taught them.
I have trained with people who know Coffman Sensei personally. They speak highly of his fighting ability, which has nothing to do with the "kumite" his current students practice. He is not a big guy, but he is supposedly really fast and strong. When Coffman trained in the 1960's the dojo fighting was not the point sparring we see nowadays. Just because he, or someone like Kise, knows "the real" they are not necessarily transferring those lessons in an unrevised form to their current students.
I trained very hard for many years under a great teacher who emphasized doing the kata as close to Seito as possible. He was a senior in Kise's organization at one time, and stated that Kise included more Shorinji Ryu aspects when training most Americans. This is very evident in Coffman's kata.
There use to be video on the S.M.O.K.A. site which showed a very interesting and solid performance of Pinan Shodan. His glide stepping for power generation (suri ashi) was smooth. That kata performance had more Seito principles than these newer kata snippets, yet was still a mixture. I think it was from decades ago.
So if someone said that Coffman was a very good Seito stylist, they were speaking of HIS brand of Seito; the way HE did karate. It seems that every high ranking sensei eventually adds there own stamp to the style. Since Coffman's emphasis was Shorinji Ryu what you see is heavily influenced by that ryuha.
I feel as though I trained with a teacher who tried to keep the Seito he learned separate from other system's influences. The kata we did, for example "Chinto" which is one of the forms on Coffman's video, followed the same "embusen" and order of waza as the video of Soken O'Sensei performing it at an advanced age. He just adapted it to his stage in life by omitting a few techniques and stances. Coffman's Chinto differs quite a bit from that version if you know what you are looking t.
In Seito the knees are bent much more than is seen in Coffman's "Seito". The shuto are different and the stances are not so short and narrow. The movements are fast and fluid and show good power. there is less arm punching and more use of gravity and koshi. Everything looks much more relaxed and deliberate in the kata I learned. There are no real cat stances, and everything is done on the toes, no heel first stepping or pivoting.
I like this guy, Medulanet, but is he attacking someone you guys wound up disliking because he was a liar and you had proof of it, or because this person lacked tact? This guy he speaks of (with the assumption that the "Seito Guy" is unaware of Medulanet's flanking attack) who use to sing the virtues of Matsumura Orthodox must have got into many of you. Even with him gone you still dwell on his words so he must be "in you" for some reason. Maybe he does know "da' real" and you guys are longing for his slant again...
That "change body" maneuver on the sparring video with the bob and weave, is not Seito. Change body involves subtler movements and gaining a "rear corner". What that guy did on video was not typical "tai sabaki". He did get out of the way though, but due to bad posture and upper body position could not immediately follow-up. True body-change involves counterattacking with tai sabaki.
Question things always, even when you think you have "the real". Matsubayashi is solid but it is still not true Orthodox. Just as Orthodox is not Matsubayashi Ryu-- fo' sho' tho'

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Train and cultivate yourself more. Post less. Be honest with what you do, who you are and what you think is "real". Good karate is rare, so if you know that what you're doing is tight, keep learning and adapting. I am forever grateful to the Matsumura Seito way as I was taught. It is a great style which takes a decade for most to even begin to get right.
Happy New Year!!!