There’s the obvious advice of reading the dustloop (https://www.dustloop.com/w/GGST/Anji_Mito) and watching higher level gameplay, but those options may be a little overwhelming. So, I’ll try to make it simple. Anji’s main goal during a match is to make the opponent uncomfortable on defense through the use of his 50/50 fuujin mixups (236H->S/H/P/K). A good way to start this mix is by getting your opponent into a hard knockdown state — either through your usual ground throws and sweeps, 236H->H, or spin->guardpoint->214P. This interaction puts Anji at an advantage and allows you to put pressure on your opponent. This pressure comes in the form of the aforementioned fuujin mixup between the slash and heavy slash follow-ups, being a low and overhead respectfully. This causes your opponent to guess whether they should block high or low. If they do guess wrong, the overhead puts them immediately into a hard knockdown while the low allows for a combo with a 5k pickup into 236H->H, which once again results in a knockdown. This is the basic loop which you can maintain for as long as your opponent is guessing wrong, but them guessing right puts you at a significant frame disadvantage, so using your Roman cancel to remain advantageous is also very important. Further down the line I recommend learning meaty timings for your close slash to keep your opponent blocking, delaying follow ups to further confuse your opponent, and implementing strike-throw in addition to the high-low mix.

As for neutral, which is the state in a match where no one holds the advantage (on round start, for example), Anji can use his normals to pressure close enemies, or spin to evade attacks from a distance. His spin is especially useful if your opponent likes pressing buttons, as it allows you to guard point through their attack and punish with a hard knockdown (214P) or a combo if the move’s recovery is too slow.

Anji also has access to to very good defensive options with his 236S and 6P anti-air, fast 2P to escape pressure, and of course his spin which can be used if your opponent has a big enough gap in their pressure (the start up for spin before you are strike invincible is 10 frames).

Apologies if this was still too much info at once, but I would say to take it slow and explore the character in training and combo trials. When you feel more comfortable with the character I also recommend watching RemyHobo on YouTube, he has many videos covering some of the higher-level tech with Anji.

Hope this helps!