This is the first level that Pigeon de Sable will appear in. When the level begins, only Snache and Pigeon de Sable will appear. Upon damaging the base, R. Ost, Mooth, and a large group of Pigeon de Sable will spawn.
Crazed Gross Cat is pretty effective against the Pigeon de Sable; when the boss appears, the Pigeon de Sable must be defeated before it accumulated and using long-range character (Bahamut Cat and Ururun Wolf) to damage R. Ost and the Mooths behind it.
Use Crazed Wall and Octopus to stall the Pigeons and max out the Wallet. Do not use more than one Octopus.
Once the money is almost maxed, spam everything. The major threat is R. Ost, but Eva Unit-08 helped a lot by killing / knocking back the Mooths. I was thinking that Octopus can help me win the stage, but it can be killed by the R. Ost easily. Indeed, at my level, the R. Ost (1 Star) almost pushed to my base but I finally killed it before it did. A Sniper Cat may be helpful, though I didn't use one.
Turn off cat cpu and sniper the cat, stall with one paris cat at a time while leveling up your wallet until you reach max money, then turn on cat cpu and, once you hit the base, turn on sinper the cat.