Backpack Hero

There are a total of 880 items in the game, so you will need a majority to reach 700. Only items encountered in Story Mode count, and you can see your current total when booting up your Story Mode file.

While the progress is slow going, here are some tips that should help you find as many items as possible.

-Items count whenever you see them selectable (i.e, when you can physically equip it). You do not need to have them in your inventory for them to count.
-Even if you are happy with your loadout, visit all shops and open all chests you come across in case there is a new item.
-Holding on to a luck ring (or other luck-based item) may offer rarer items you haven't seen yet.
-Unlocking items from town will not automatically count it for your items, but it will add them to future runs. For this reason, it is good to keep note of which items to look for during your run (for new item ingredients) and keep it until the end (or preferably give it to Parcel) so you can unlock new items.
-Keep progressing through the story. Some items become available with further progress.
-Play as the other characters. Some characters have very unique items in their runs that you will only encounter with them.
-If you have the resources, unlock game modes from town that offer unique starting items. These items will count as soon as you start a run.
-Don't forget about Cursed items! While you may be hesitant to open a cursed chest or play a risky mini-game, there are many unique cursed items to find.
-Be sure to play all the mini-games you find. They tend to have pretty unique items. If you see something as a potential prize that you don't think you have possessed before, be sure to aim for winning it.
-Again, only Story Mode counts. Your quick mode game items won't add to your total, even though it is tied to your save file.