Final Round (Hard) is the final stage in Sophomore Summer.
Final Round (Hard) is fairly easy compared to most of the other Collab. event stages so this shouldn't be a problem unless your cats are underleveled. True Forms for some Normal Cats are recommended like Macho Leg, King Dragon and/or Jamiera Cat to make the job easier when fighting this stage. Rocker Cat is advised because of his high health but you don't need any gacha cats to beat this. If you are a beginner, this level may be slightly challenging.
For beginners, if you don't have Bahamut Cat, bring True Valkyrie Cat as a substitute. Though here, even with a Level 20 Crazed Bahamut, you can't one-shot a Hater/Grim Hat so this level may be somewhat tough unless you have Crazed Bahamut. If not, you have to rely on spamming to get the job done.
Take it easy when spawning Cats in the beginning because you don't want to start the wave of Grim Hats when True Valkyrie Cat/Crazed Bahamut Cat/Uber Rare isn't on the field.
The moment your cats hit the base, the wave of Grim Hats will spawn. Spam everything you have because Grim Hat has a single-target attack and all of them have been synced so you can overwhelm them. Another one will spawn quite a while later so try to finish off the wave as quickly as possible.
Once you defeat the wave and/or (depends) beat the extra Grim Hat, no more will spawn. If you finished off the horde without the extra one appearing, the extra Grim Hat will still pop up at some point though it may be trying to hit your Cats while you're attacking the base (that all depends how quickly you defeat the horde). Spam everything and the Rare Cat Akio Yabe is certainly yours!