Hidden items[edit]
Each secret is an invisible box with a bonus inside. When you hit the invisible container, you will hear a sound. Three hits is enough to get the bonus. If you used ninpo, it will deal damage to all enemies and containers as well, revealing the hidden item.
Stage 1-1: katana[edit]
When you jump from the high block, you will see the box (kusarigama inside) and a monkey below. It seems like there is no reason to jump down, but actually there’s one. Jump down, get rid of the monkey and walk all the way to the right. Invisible box with katana is in the corner below the railing.
Stage 1-3: bombs[edit]
See the fifth big wheel? That’s the very first big wheel right after dual wheels. There are bombs right in the center of it.
Stage 1-3: scroll[edit]
You need the eighth wheel. That’s a wheel with two platforms. It locates in the middle of the screen; no parts of it are hidden up or below the screen. The secret is right in the middle of the wheel.
It’s no so easy to get it, however. First of all, get rid of the sniper on the right, or he will interfere you, dramatically reducing your chances to get the secret. You need to jump on the platform and hit the invisible box without falling down, but that’s only a half of the problem. The scroll falls down even through the platform and disappears below the screen, so you need to be quick to grab it. You can sacrifice part of your stamina and use ninpo, but your timing still needs to be good.
If your weapon’s level is 3, you don’t need this bonus. Just ignore it.
Level 3: bombs[edit]
As soon as you finish climbing ladders for the first time on this level, don’t move forward. The secret is left of the ladder, next to the top of it. Just climb down a little and strike left. You’ll get bombs.
Level 3: healing potion[edit]
The secret bonus is right before the boss. After the third (and final) set of ladders move right until you see the box with katana. Climb down. The container with healing potion will be near the right wall.
Stage 4-1: bombs[edit]
When you’re climbing up under the heavy fire of enemy mortars, pay attention to the satellite dishes. Hidden bombs are in the middle of the third one.
Codes[edit]
First of all, all codes work only in American version Shadow of the Ninja and Japanese version KAGE. There is no way to activate them in the European version Blue Shadow.
Entering the code[edit]
On the title screen press 
. If you did it right, you will hear corresponding sound. Use any code(s) from below:
Level select[edit]
Enter the main code. Press some buttons on the first and/or the second controller (see table below), then, without releasing these buttons, press 
on the first controller.
| Stage | First controller | Second controller |
| 1-2 | none |
|
| 1-3 | none |
|
| 1-4 | none | +
|
| 2-1 |
|
none |
| 2-2 |
|
|
| 2-3 |
|
|
| 3-1 |
|
+
|
| 3-2 |
|
none |
| 3-3 |
|
|
| 4-1 |
|
|
| 4-2 |
|
+
|
| 4-3 | +
|
none |
| 5-1 | +
|
|
| 5-2 | +
|
|
Or you can just press to start from the very beginning.
Invulnerability and nine lifes[edit]
Enter the main code. When entering the level code (or pressing to begin from 1-1), also press and hold down on the second controller. You’re now invulnerable to all attacks except for bottomless pits and using ninpo. Moreover, you will have 9 lives instead of 5.
Sound test[edit]
Enter the main code. Press + on both controllers and, without releasing them, press . Choose any character, and you will get to the secret menu where you can listen to all in-game music.