When you enter the arena keep your eyes on the original Stone Monkey cause hes the one youll need to focus first. The trick with this fight is staying at medium distance to bait out his jump attack, which you can dodge and punish with a few hits since he takes a moment to recover. Maybe interesting that the Plantain Fan actually works really well here cause the tornado keeps him locked down long enough to get some good damage in.

Once you see him starting to split up thats when things get tricky, but dont panic. The clone system works like this - one will always be attacking while the other rests, and hitting the resting one is a big mistake cause then youll have both coming at you. A good thing to remember is that your Cloud Step ability lets you get away quick if things get messy, and focusing your attention on just the active clone makes the whole fight way more manageable.

The second phase gets pretty wild with all the shockwave attacks, but if you keep your distance and watch for the tells you can dodge through them and get some hits in while theyre recovering. Tip for you - save your transformations and strongest spells for when both clones are out cause thats when youll need the extra firepower, and dont forget that your Plum Fan can stun them both if you time it right giving you a nice window to deal some damage without worrying about getting hit from behind.