The Fuujin Guessing Game
Fuujin is a defining part of Anji's gameplay, and learning what to think about while using it is a very important part of playing him well. Fuujin's followups all are punishable in some way, but in order to punish one, you are opening yourself up to another followup. This fact about Fuujin is the basis for the guessing game behind it, as it is based around you making the opponent think you will do one thing when in fact you will do another and punish the opponent for thinking so. The mindgame behing each followup works something like this:
Nagiha: Fuujin's guessing game primarily revolves around Nagiha (S after Fuujin). Nagiha is the safest followup Anji has at his disposal in this situation, it is about minus 5, meaning that he is essentially safe thanks to the move's high pushback. There is a wide cancel window on Fuujin, meaning that you can delay Nagiha for frametraps and catching jump startup, granting you at worst a soft knockdown, which leads to a repeat of the Fuujin situation. Once the opponent has started to block Nagiha to let your pressure end or is trying to punish Nagiha by instant blocking, you can move on to using the other followups.
Shin: Ichishiki: Now that you've conditioned the opponent to respect and play around Nagiha, you can now more safely use Fuujin's other followups. The next safest option you have access to is Shin: Ichishiki (P after Fuujin), which will reward you with plus frames if the opponent blocks it, allowing you to throw out a f.S or 5K to stuff an attempt to poke out from the opponent and continue pressure. Midscreen this followup is weaker as it's hitbox is narrow and following up after the move is inconsistent. The point of using this move is primarily to pester the opponent into trying to jump up and either punish you or escape the situation. Once they start to do so, you can return to using Nagiha to stop this behaviour. Eventually, the opponent will be torn on what to do and just start blocking, which is where the other two followups come into play.
Issokutobi: So what do you do when the opponent is just downbacking? This is where Issokutobi (K after Fuujin) comes into play. Issokutobi moves you directly next to the opponent, allowing you to land a grab and go into butterfly oki. This followup is where you can start to put yourself at some serious risk, since if the opponent is looking out for this followup, they are able to punish you on reaction. This move is a prime example of what the Fuujin mindgame is about, as while this move is technically reactable, it is not reactable enough to punish every time unless the opponent is looking out for it specifically, which allows you to get away with all of the other possible options. Using this when you think the opponent isn't prepared for it is essential to keeping the opponent on their toes and opening themselves to the other followups.
Rin: While not useless, Rin (H after Fuujin) is certanly the followup you should abstain from using the most. It is a reactable, very unsafe on block and whiff overhead that loses to mashing and even sometimes jumping. Rin should only be used as a surprise tactic to call out people downbacking and looking out for Issokutobi a little too much. Make sure to use this sparingly, as it will work rarely against people who know what their doing if you abuse it.
Nothing: Sometimes when you have conditioned the opponent well enough with your Fuujin followups, it is possible to get away with not using a followup at all and resetting pressure from there, even though Fuujin is minus 16 on it's own!. Usually when this happens, it can signal to your opponent that they are being too patient with you and can persuade them to be more aggressive.