Akiha's basic combos are harder than most characters, it'll take you a bit to get her bnb down in its fullest. When you learn how to hitconfirm 2AA into 6C instead of 2B though, it really does improve your game. Anyways, yeah, tk.2C is literally just 8 and then on the first cancellable frame, hit 2C. Or well, try to.
When is it low enough? When you can combo off of it.
Actually, I start the combo with 2a. I'm guessing Psylocke had it start as 2a and not 2aa because maybe that'd make you move too far away from the opponent. Currently, I'm working on getting those second j.b hits in the air, key seems to bringing out the j.c quickly. I'm noticing Frank the Tank has a last j.c after the airdash, but even he says it's difficult. After that, I'll work on the airdash, then putting in a tk.ribbon.
I was going to ask if there's any real difference in Psylocke's version of the ground portion, and Frank the Tank's version, but then I noticed they had the same hits, same button, just different order. Considering how ingrained Psylocke's version is in my head now (can do it with my eyes closed; actually can do the entire combo minus the tk.ribbon, the second j.b hits, the airdash, and that final c hit after the airdash), anyway, I'll be sticking with Psylocke's version.
BTW, judging from that Benny1 mentioned, should I perhaps try starting it with 2aa? As in 2aa6c4c5c2c etc.?
Also, if Akiha's BNB's are harder than most (which is what I heard), what would be an example of a character with easy BNB? I used to play a little Tohno Shiki, but I never tried combos with him and I've never really tried any other character (not that I'd ever switch from Akiha at this point; Yukinose's Akiha combo movie was what got me into MB, combining my interest in the long combos and that my favorite Tsukihime character is Akiha).