Here's a video I have versus JJJ's Mitsu at a online tourney last night. I got hella bopped so I need some tips versus Mitsu if possible. I also used switched to Aeon around 5:50 so you can pay no attention to that if you wish.
I'll try to help though I am no where near a high level player and have been rugi rolled several times in the past lol.
You have to very careful with attacking and moving because Rugi has his infamous 4B and really good (probably too good) tracking and damage. You should zone him to avoid his 1A, 2KB, AA, etc. If he gets in, land your 2A and throw/mixups. Try to step and bait out his high horizontals and 4B them to land good damage. Know what you can punish. You can also back step and do 236B like you did.
When you block one of Mitsu's moves and he enters MIST, quickly buffer 66B to beat all of his options and land Prep A+B and laugh at him. His MST A+B can GI 66B but since it enters Prep, your Prep 4 will re GI that and you can nail him with Prep A+B or Prep KBE at the cost of meter. Basically, show him who's the bigger badass lol.
If he does 1aB which lasts more than a second, you shouldn't be getting hit by this lol. It's the perfect time to QS it and get damage off of him. As for his 4B, well you'll just have to be conservative in your attacking pattern, as it can evade and hit you even when Mitsu is at negative. You can 8wr to avoid it and I think Raph's 44B can beat his 4B but Im not sure.
You basically have no other options against 22B haha but to watch out for it (avoid being too linear) and block or JG it. Also, watch out for his 6B moves and FC 1BB. Be patient and block FC1B and then punish with 44A+B or QS it for a back throw.
For Mitsu's 11BA series, you need to manually duck the second hit and watch if you enters mist, does the last B, or stops there and act accordingly.