he is so cool sadly not hard

Simple strategy, use two to three gust talismans to reflect his bullets the whole fight, then use shuriken and kunai to pull him out of the air for a good two or so seconds opening. They also help interrupt his specials, the fire balls and the fire wind sickles.

Holy crap this fight is tedious.

He seems to have low corruption resistance and high elemental resistance. As a onmyo switchglave character I put most magic aside and just used seething dragon unbuffed and barrier talisman with the snake boss core to really mess with his stamina. As long as he is on the ground his AI seems to be mostly baseline human and as such most stunlock tactics against human minibosses should work pretty well.

Smithing Text: Hikoemon Ichimonji dropped for me in (The third word), so you can get it in both missions.

This guy was so badass he ended up in both games as boss multiple times

while trying to get Yara I raked in smithing text for Hikoemon Ichimonji, Dual snake headed tonfa. Sohaya tsurigo
No Yata or Hacco yet

He seems to resist water less then the other elements

It seems the Devs found his exploit in the last game, he is no longer downed for a grapple if you hit him while he is in the air with a spear, take care when fighting at a distance as he has an array of attacks that can match your arsenal. His spirit attack is also easy to avoid but very dangerous should you get caught in it as it will also deal fire damage over time.