I don't know which situations you have trouble with, so, I guess I'll give you what I mostly watch out for when playing them.
Tina.. Well.. Don't use holds unless you really have to. Her grabs are crazy high. Don't use low often because she can crush them easily with a lot of her moves. She's also fairly safe, so, this is where you'll have to use deception and try to confuse your opponent so you can get your momentum going.
Lisa.. Don't let her get too far because at a distance she controls the pacing, and use high attacks only at the right times, ie when she does flying/jumping attacks. She can crush a lot of moves, so, up close you need to be careful, but in general low and mid moves can beat her out, since she's not that fast.
Bass.. You outspeed him. Use that to your advantage. Watch out for his offensive holds and his lows. If you can, stay close. Note that you also need to learn specific juggles for him due to his weight. Same goes for Bayman btw.
Bayman.. He can be quite evasive. Be careful with that. Watch out for his tank roll. Try staying close since he has great moves for mid range that can crush most of Kokoro's arsenal. Watch out for his parry. Delaying your strings helps quite a bit.
Rig.. I wouldn't know what to tell you. I barely know him. All I know is that you need to focus on holding/sidestepping mid and high kicks. Watch out for his sitdown stuns.
Eliot.. Slow escaping is very useful against him. He's another one with a parry, so be careful with your mids. I guess lows are quite effective against him, however, Kokoro lacks them, so, you'll have to find some other strategy.
Gen Fu.. He's a nightmare in general. He can crush a lot of things, has a mid parry, is super fast up close.. There is not much I can say, other than learning your opponent's patterns and exploiting them. Gen Fu outplays Kokoro in pretty much every area, except maybe long range.
