True ancient fact: when ninjas can't use horses as transport, they use surfboards. The opening stage of this round has you heading across the sea, where some soldiers on hoverjets will keep flying in. These troops take 3 standard shurikens to destroy, and they will drop off mines on you. Whenever you see an "!" in this stage, it means there is a ramp coming up. When you hit a ramp, press the jump button.
Sometimes the enemy troops will come from the left of the screen instead of the right, whenever they do this, they will use a machinegun burst. You can avoid this by jumping over it. As mentioned earlier, jump whenever you hit a ramp as you will be able to collect some items and avoid some mines planted in the sea.
When you've gotten far enough across the waters, two small robots and one large vehicle will appear. One of the robots will fly high into the sky, whilst the vehicle will also move way across to the right. However, the remaining robot will challenge you. It is armed with a rifle and a shield.
The robot is the sub-boss of this round and will attack in three ways: firstly, it can fire mines at you. Secondly, it will fire a shot at you, which breaks apart into three shots, so jump out of the way and try not to get trapped in the corner. Thirdly, it will sometimes try and dash into you.
The robot can also use the shield to deflect your shuriken, but as it can be hit anywhere this sub-boss isn't very tough to beat and you should be able to take it down quickly. The next stage will then start, which ditches the surfboard and is a more typical platform affair.
Along with the ninjas, another type of enemy in this stage are some warriors who have mastered fire magic, allowing them so shoot streams of flame at you. They take three standard shuriken hits to kill. Make use of the pipes around this stage, as you can use them to stay far above the waters.
The ninjas you encounter here haven't changed their tactics since the first round, but there is a new ninja type here: flying ones. These fly around in circles and throw shuriken at you, which can be dangerous here as a hit could send you crashing into the waters for a cheap kill.
Towards this end of this stage you will have to use the smaller pipes to get around. There is another new enemy type to watch out for on the pipes. Small ninjas will crawl around them, and will try and stab you with their claws when they get close. They only take one hit to kill, but can move quickly when they see you. Another hazard is on the pipes themselves, as there are several valves which shoot blasts of steam.
You will also come across some parts where you have to jump from barrel to barrel to get across the waters, look out for the flying ninjas here as they stand a good chance of knocking you into the sea if you don't kill them first.
Eventually you'll get through the pipework and come to the end of this stage. The boss stage then starts, and it is a fight against the large vehicle seen earlier.
This boss is the toughest one yet as it has several different and powerful attacks. It can shoot lasers in bursts of three blasts from the cannon, and will also send out mines. Keep firing at the cannon to destroy that first.
The boss fight will be far from over after the cannon is destroyed, as the boss will change form and reveal that it has another cannon. Keep firing at this new cannon, and jump to avoid the shots it fires.
The boss will sometimes move across the screen and fire rockets at you, these can be destroyed with the dive attack, or by using shuriken. Once the second cannon is destroyed, the next target to take down is the shield.
In additional to using mines and missiles, the boss will start using another attack from this point. It will charge up a powerful laser blast they you'll have to jump high over to avoid. The boss will also sometimes move across the screen, fusing a machinegun to fire shots at you.
Once you destroy the shield, the boss will continue to function, but can now be hit from anywhere. It will still use almost all of the same attacks it has had throughout this fight, but since it is so much easier to hit it won't take too long to completely destroy.