There are 5 kinds of items in Ninja II, as well as 2 special Bot items (Bonzebot and Errandbot) and items that pop out of . Items can be bought in pretty much any item store, but some will not be available until later in your adventure. Errandbot can buy any item for you, but the cost is doubled 0_o!
There are also some items found exclusively in battle and 2D special stages.
Consumable items can be bought in stores, and used in battle, boss battle, overworld, town, dungeon... pretty much anytime our ninja boys aren't busy talking to someone.
An essential item for long trips, the Sweet Bun is the Medical Herb of this game. It can be used inside or outside of battle, it recovers around 40 HP, and you can carry 8 at a time. They sell for 20 Sen, which is quite inexpensive!
In the screenshots below, look at the HP value of Jack. The first is before using a Sweet Bun, the second is after.
Some enemies in Ninja Boy II have projectiles that can turn your character into a stone statue. In the event that you become petrified, a Capsule can save the day! Using one in battle will cure petrification. Also, if your teammate has been petrified in a Boss Battle, simply use a Capsule to get him back.
Cupsules sell for 30 Sen, and you can hold 8 at a time.
Boo Bombs are a fun little item. They can be used in battle (I don't recommend wasting them that way), or used outside of battle to blow up weak walls and clear paths.
Boo Bombs are a steal (not literally) at 10 SEN each, and you can hold a maximum of 8 at a time. Below are some screenshots; one of a Boo Bomb being used in battle, and one of a Boo Bomb being used on a weak wall.
Though more expensive than a Sweet Bun, Meat Buns refill all of your HP! Not too shabby! They sell for 300 Sen and you can hold only on at a time, due to their tendency to fight each other if two are carried together.
Non-Consumable items are usually given to you by someone or something, and are used outside of battle. The plus side is that they can be used as much as you want!
Due to my lack of access to 2 Ninja Boy game cartridges and 2 Game Boys, I cannot truly confirm what this item does. From my experience with the SNES game though, I can guess that this item revives the other player if he dies.
You'll receive Bonzebot after visiting Ragyu in White Castle.
Are you in need of a Meat Bun, but you're miles away from the nearest Item Shop? Errandbot can fix that! Simply call him up on the overworld or any non-dungeon, non-battle screen, and order as much as you need! Keep in mind that each item sells for twice as much as before!
Errandbot is given to you by the Fortune Teller in Flotown.
When you acquire this ship from Dr. Justice, it will appear as an item in your inventory. Selecting it while on a planet's surface will allow you to fly across the planet. Keep in mind enemies will still attack you, but also keep in mind that flying over mountains and cliffs is a much easier way to get around.
Battle items are found in the P blocks lying around on the battlefield. Crack them open, then burst the ? bubbles that pop out to pick them up. You never know what you're gonna get! 8P