now what's wrong with using medicine. Give me a break 
Well, Medicine's EX-attacks, that is attacks that get unleashed upon the enemy through combos and the destruction of spirits, are these poison clouds that don't harm you directly but slow you down when you are in them.
The Lunatic AI usually doesn't move any more than neccessary, sitting in front of the bullet until the last frame before it would get hit. Then it dogdes the bullet with full speed and extreme precision.
Now, if the lunatic AI is inside a slowing poison cloud, this method will fail very often, leading to a (comparatively) easy victory even on lunatic. Something similar but not as drastic happens when you use Aya's high speed EX-bullets against the AI.
So, on topic:
After a few humiliating tries on UFU Extra failing hard on Kogasa and sending my history for Heian Clouds to 3/6 *cough* , I somehow improved by several degrees, not only beating Nue for the first time with MarisaB but also doing it with 2 spare lives and capturing Rainbow UFOs and Nightmare of Heiankyou for the first time.
I still fail hard on the Green UFOs without SanaeB, though. :V