I think this boss is call to the Guardian Ape boss from Sekiro. However, unlike Sekiro, there are no cheeses or glitches in this game, or I haven't found any. The boss won't give you enough time to predict his moves & implement all the tips & tricks you come across on YT. The only way to kill this boss is to keep fighting him it until your "Qi" (actual mind) gets accustomed to him & aids your dexterity to finish him off. Luck is also very important.
Half of the fun of a multi-phase fight is not knowing it's multi-phase until you've beaten the first one. Personal opinion, but in sekiro there's a multi-phase fight that blew my mind and honestly made the game for me, because I didn't see it coming.
Not knowing it's multi-phase from the start feels a bit cheap to me. I think this is because I often burn all my resources (not expecting the second phase), die, then restart and kill it.
At 6:29 while you have him immobilized, you get hit by something. Can anyone tell me what it is? I have died three times from this same mysterious attack and nothing I have found online can tell me what it is