Source: Youtube Encountered: Boss Strategy: The best weapon to use are Ranged such as Bows and Rifles. You can't move for a brief moment and then you are dropped from a height. Remember to not push with your hero on the boss because Umibozu moves away from the pier during a few attacks which means that William can fall into the water. Remember to dodge to the side on all her ranged attacks. Always do yellow and red if it fails kill yourself and do blue.
You can see your proficiency for each weapon type in the additonal stats. You will need to attack him in a gap of few seconds. You could brute force it by overleveling. For this fight, you should prepare two katanas because their attacks keep a balance between attack speed and damage. Fire is his only weakness while he is completely invulnerable to attacks enchanted by water. That you can effectively do this on almost all bosses is what makes it kind of ridicolous for me.
It will then turn around and try to attack you with its mouth. The nioh duo was really hard, but doable if i focused on the aggressive one. Simply complete all missions and this will unlock. When that happens, pop your living weapon and go in for the kill. When it has weakened, it will start throwing bombs. This makes double bosses a hell of a lot easier. After that the boss goes underwater and moves closer to one of the pier's edges.
Complete the mission and then buy the mystic art using skill points. Some weapons and accessoires provide bonuses on proficiency so you can max them out quicker. When he uses dual katanas the attacks are harder to dodge. After that, retreat and wait for his next attack. You don't want to trap yourself! There's a tight rope walk here on range: if you get too far away, watch for a back flip animation warning that Hino-Enma is about to quickly charge forward. Spear Master Acquired mystic art for the spear. For each quest you need +5 magic points 5 magic for Novice, 10 for Adept, 15 for Veteran, 20 for A Greater Harmony.
Keep attacking until you make good enough damage. She is very tough in close combat. They can be selected on the far left of your world map the hub area from where you select missions. Use dual katanas in low stance with a fire effect. It unlocked for me after 6 missions, too. Once his health gets below 40%, attack him with a living weapon to finish him off.
Note that the order of each element per head in a clockwise fashion is: Wind, Water, Lightning, Fire then finally Earth. Keep attacking the feets and there are crystals around that you can use to charge your living weapon. This can make it a bit easier to locate them. As soon as you see the move set of the boss, the fight is pretty much over. You should use fast attacks because the boss has a weak spot that allows you to deal critical damage with each hit but more about this later.
If you take a few hits, it may kill you. The spear can easily hit him from far away. You can still use soulstones to power it up again. Hotsprings are pools of water that you can bathe in. Dodge the attacks until he stops swinging. Keep pressing the dodge button in order to get up from the ground.
There's also more room to run around than in the previous boss fight, so you have a better shot at staying out of range of Nue's lightning breath attack. I would rather compare it to Onimusha 4 Dawn of Dreams and Ninja Gaiden. When his health is below half, Umibozu will jump on the pier on which you stand. Living weapon is extremely important against him. Instead of lightning breath, he may summon lighting strikes from the sky that chase after you, regardless of your distance. Repeat this and he will die very quickly.