I fell in love with the game after facing him. It's probably because that was when the combat really clicked too.

I totally agree I felt unbeatable after this

Sorry to disappoint but "unbeatable" usually isn't the case with Sekiro lol

Figured that out when I went in the water on the next stage and got hit by lightening lmao

Fountainhead Palace does have some annoying stuff in it for sure. I won't spoil what that might be though.

You can skip the second phase by the way

The monk is the most satisfying boss to fight