After the Boss appears
Since Sunfish Jones outranges all Normal/Special Cat Units, and has a 30% chance to slow any cats hit with his attacks, the best way to win this is using tanky short ranged Cats and luck. Both types of Titan Cat are useful because they can survive multiple hits.
An alternative would be to use a well timed suicide bomber such as Awakened Bahamut or Kalisa.
Strategy 2 (Ft. God Emp. Sodom)
Line up 1: Eye of the Storm Catcombo
Special Items: Rich Cat (Helpful)
Method: Fill up your wallet and bring Sunfish Jones out of the base. Spam everything in line up 2 until sunfish dies. If you run out of cash stop spamming everything except for Ramen Cat until you can start spamming again. After that kill the base and you're outta there!
Strategy 3 (4✪)
Line up 1: 2 Unit Atk/Def Cat Combos
Line up 2: Jiangshi, Ramen, Maximun the Fighter, another tank like Zamboney (Delivery Cat is ok too) and A. Bahamut.
Start spaming Jiangshi and Ramen, whenever there are 3 gorys, let them get near and destroy them with A. Bahamut. That's all, eventually Sunfish will die