The Boss Kettle for this mission can be found directly in the middle of Suction-Cup Lookout, under the kettle for mission #8 Spinning Campground.
Gameplay
Boss Appearance
The Octo Samurai resembles an Octoling but much larger in size and more masculine. The Octo Samurai has a heavyweight and round body that is similar to as a sumo wrestler, has small eyes, and sports a tentacle on the back of his head in a ponytail. He wears a black leather motorcycle jacket with golden embroidery on the sides and a print of DJ Octavio on the back. He carries a weapon that is similar to a Dynamo that can change positions vertically or horizontally to the handle, which Sheldon calls "The Octocycle". The weapon he uses can be flicked vertically and horizontally and can be used as a vehicle that is used to rush at Agent 4.
Walkthrough
In order to defeat the Octo Samurai, you must splat it to make it drop its Splat Roller on the ground.
The roller grows into a larger form and a tentacle pops out of it. Attack the tentacle 3 times and you win.
Phase 1
The boss will fling its Splat Roller in a similar fashion to inklings, but has a very wide range.
The Samurai can also get on top of his weapon and charge towards the player, leaving behind a wide trail of ink. If he gets a direct his, its an instant Splat. The boss takes a break every time he does this, letting the player get in free hits. He always does a backward jump before doing his charge attack.
Phase 2
The Octo Samurai does everything he does from phase 1, but he has two new attacks:
He jumps towards the player and does a vertical swing with splat roller.
He quickly spins around with his roller leaving a circle formation of ink. A direct hit is an instant splat.
Phase 3
Most of his attacks get more vicious, and he has a new one:
The Octo Samurai performs three, extremely long ranged vertical swings.
He chases you when he does his charge attack. He still takes a break after this.
He will always swing three times in a row when he does his regular swing.
He always follow up his jump attack with three vertical swings. These swings are not has long ranged as his other vertical swing attack.