Strategy 1 (Overkill)
Spam front row and drop a ring girl cat to halt and deal with initial wave of peons, all the while build up the worker cat level. When under control let your pack get to the base and die, save money.
Then bring in Shingen and start meat shield spamming, drop Mekako and bring in the other 2nd row cats, better to save Bahamut for a clear shot at the boss but not critical.
I'm quite new to the game and this was my first shot at this stage, I realise this strategy is very dependent on specific cats but most are, adaptation is always possible. Good Luck!