Sorta a random, maybe outdated question haha, but I've just been googling a lot and not finding the answer so thought I'd try here. Also, possible spoilers for people who didn't read original series so look away!!
It seems that the general consensus for why Sanada didn't use Muga no Kyouchi until nearly the end of the match with Ryoma (original series, Kantou tournament) was because he didnt like it; something along the lines of he didn't like imitating weaker players. Where was this actually stated? I didn't read it anywhere in the manga (unless I missed something). Perhaps one of the fanbooks/guides?
Last edited by Kaoz; September 24, 2012 at 08:11 AM. Reason: added prefix
Since apparently nobody else knows either, I believe there is no official statement to support that, or at least I couldn't find anything in the PPs and I don't remember reading it in any databook.
It's just a theory as far as I know.
Perhaps one of those pages at the end of the chapter when Konomi draws a little pun or holds a mini Q and A with a reader's question and then the characters answer it.
Sanada wanted to teach Echizen a lesson, so he wasn't trying to win. Sanada started to dominate Ryoma by using one technique at a time. When Echizen was thwarting his plan by overcoming these techniques to the point of even using muga, Sanada had to one-up him again by returning the favor. It really had nothing to do with tennis. It was a battle of authority. Echizen overstepped his boundaries by challenging the one on the throne, and Sanada had to put him in his place. It wasn't until he saw Echizen take the chance of hitting a 1/100 chance Cool Drive that Sanada finally gave Echizen his respect, and ultimately handed over his authority as champion. This was the most pivotal moment in the entire series (from a literary point of view) for that reason.
That is why I think Sanada's use of muga was simply a means to one-up Echizen directly, in a once-in-a-lifetime battle of authority. This is why it has never been done since. I hope my interpretation helps. Sanada has been my favorite character since he was first shown, so I should know a thing or two about him.
I recall Sanada saying 'why would I want to imitiate inferior techniques' during one of the side Q&A session. Since his moves already counter pretty much every move out there at that point in POT, there's really no point for him to copy anyone else's moves. Also, at that point Ryoma has seen Fu and Ka, which counters the vast majority of normal special moves. Zan seems to be just another name for 'extended rally' which seems to be what's happening anyway. Rin counters Tezuka Phantom (and zone by extension) and Data Tennis type moves since it was used against Yanagi, but none of his moves seems to require a special counter so I assume the reason it's used is to deal with Data Tennis type attacks. Muga hasn't been shown to be able to replicate Data Tennis and that sort of make sense (you can't just reflexively know there's a 95% chance the ball will bounce one way or another) and of course Tezuka Phantom doesn't even exist at this point so in the pool of special moves there's nothing that can't be countered by Fu and Ka, which Ryoma knows at that point Sanada could have used.
Of course that means he used Muga just to glow in a different color and wasted energy for no reason but it's not like people have logical motivations to play tennis in POT. In fact it's pretty strange that Yukimura and Sanada mastered Muga because there really isn't a point for them to ever copy anyone else's moves. The only move they'd have a reason to copy would be World of Ice (except I don't think you can copy eye powers) or Tezuka Phantom (which would trash your shoulder) so it's literally useless for them to have that ability.
Sanada stated that he tried to replicate Tezuka Zone with it but failed. There's your motivation.
That aside, in the match between Echizen and Kirihara, it's also implied that the user's power and speed increases in Muga, so even if you don't copy anything with it, it can still be used for that.
Given how Muga is pretty much used exclusively for copying moves, I think we can assume the increase in stat is not the primary motivation for using it in light of its alleged cost. Of course, I'm sure Sanada is more than capable of keeping up Muga the entire match since he has the highest endurance out of all POT characters (he outlasted Atobe). Of course the whole Sanada versus Ryoma is kind of uncharacteristic for him to begin with. If Sanada is really the guy who has to win at all costs then he should use Muga as soon as he starts losing control of the match, as opposed to using it when Ryoma has a match point.
The real problem with Muga is that World of Ice did not exist until Muga ceases to be anything special. Yukimura and Sanada are all around players who are more than capable of countering every move head on, so Tezuka Zone wouldn't really do anything useful for them. It's pretty clear that in POT (not NPOT) you need Tezuka Zone to defeat World of Ice if you're actually playing tennis so had World of Ice exist since the beginning, that'd be the proper motivation to master Muga in hoping that you can one day replicate Tezuka Zone because you need it to deal with World of Ice. But of course, World of Ice didn't exist until quite late in the story and without World of Ice, there really isn't any motivation for either Sanada or Yukimura to want to learn an 'inferior move'. Remember, originally in the match against Rikkaidai it was said imagine the Rikkaidai team as if they have 7 Tezukas. Tezuka's power level seem to be retconned to Sanada tier as POT progresses, but at the time Sanada used Muga, Tezuka was definitely lower tier than Sanada so there's no reason to copy a lower tier move.
---------- Post added at 03:14 AM ---------- Previous post was at 03:03 AM ----------
After thinking about some more I think the problem is that as crazy as Yukimura and Sanada's moves are, the 3 doors are even crazier and there doesn't really seem to be a logical way to explain why 2 guys with presumably the highest overall stats in POT would ever lose a game while having hack-like moves. In fact both of them almost sounds jealous when they talk about how the first 2 doors are useless. Why work so hard to invent a move to counter the first 2 doors if you can learn it yourself? They're supposed to be the two of the three guys that understand it better than anyone else, and apparently neither has ever opened a door.
Honestly it'd make more sense if it's said somewhere that descendents of Sanada Yukimura are not allowed to open the 3 doors because Ieyasu Tokugawa used the three doors to conquer all of Japan and framed the Sanada family, or something. It literally makes no sense why someone with a title like 'Son of God' can't even open a single door.
Stuff about Akaya and DM is irrelevant from what I can tell, so I'll leave that as it is.
Given what Yukimura says after Echizen achieves Hyakuren, I doubt he/they would even want it, since guess what, he doesn't have a Zone like Tezuka does. Saiki seems to require a great understanding of how to read a match which they don't necessarily have. Rikkai's entire philosophy goes against what's needed for TnK.