Collect the gold Oboro Clan Coins during the game to unlock bonus options in the extras menu, including level select and movies.
Collect 30 Oboro Clan Coins during the game to unlock Moritsune. Moritsune is Hotsuma's brother, and is stronger and faster. However, the Akujiki sword will drain him more.
Collect 40 Oboro Clan Coins during the game to unlock Joe Musashi. Joe's sword damage does less than when playing as Hotsuma, however his shurikens are unlimited in number, do more damage, but do not stun. Also, since he does not use the Akujiki sword, his energy does not drain constantly.
Collect 50 Oboro Clan Coins during the game to unlock the VR stage.
Successfully complete the game on the normal difficulty setting to unlock the hard difficulty setting.
Successfully complete the game on the hard difficulty setting to unlock the super difficulty setting.
You can either defeat the five or six dogs then attack him with the glowing Akujiki sword, or just run past the dogs and hit him from the side. You can hit him about three times before he retreats into his take-out box. Hitting him in the side causes more damage than hitting him from the front. He recovers after he returns from hiding.
This is the spider boss, by far the easiest. Dodge its attacks and wait patiently for its little hench-spiders to pop out. Quickly dispatch all four and head for the Boss. It is absolutely necessary that Akujiki is glowing red. Jump up at the Boss and slash at the weak spot on its back. If done correctly, you should go into a tate in mid air, and all five enemies will die.
Wait until all of the henchmen appear (about eight spheres should appear at the top right of the screen). Then, kill all of them as if you were going for a Tate. Akujiki should turn bright red after you kill seven of the henchmen. The difficult part is getting the Boss to stay still after your sword turns red. This may take a few attempts, but you will get a huge Boss bonus for killing them with one hit.
If you can wait until the Boss lets out the seven little heads, kill them to get a full powered Akujiki. Then, just slash the Boss once and he will die.
Attack the crows (the things which shoot out fireballs). Wait until you have about eight crows at once. When you defeat the crows, you should have a pink waves around it. Attack him when you reach that level. Any other color will result in no effect. Keep doing this and you should defeat him.
A rather easy way to defeat any Boss in the game is to wait until seven or more of their helpers have been summoned. Basically, when you see eight or more of those orbs at the top right hand side of the screen, perform Tate and any Boss in the game will die. Note: You will not get seven or more minions to spawn at certain Bosses, such as the two helicopters and the giant spider at 3B.