Ninja monkey does the job pretty well.
Monkey king just increases the combo count by 1 , which you dont need at all, since Sai beasts+Main mystery is the trick here.

Earth mains can do the highest score in SA using this method, dont think any other main can beat that score. If you have sailor sakura, this will work out better. Since sailor S mystery has 1 round less cd, you c*e her more frequesntly and it helps to finish with max health.