This is a guide about how much damage everything in the game does. I'm going to keep it as quick and dirty as possible becuase if you're reading this guide all you care about is how much damage stuff does.

Keep in mind these damage values are RELATIVE damage values, based on the damage of the uncharged bow shot (so something with a damage value of 2 does twice the damage of the uncharged bow, 3 does triple the damage, etc). These values were not taken directly from the game's code, but for all intents and purposes they are just as accurate.

Important message: Please check my work! Below is my testing method (you don't have to do the same thing, but it's there if you want it). I made sure to double check everything but if you notice any inconsistencies or errors in my data please let me know!

Testing methodology:
My testing method was based around attacking the giant radish enemy in the forest (the one guarding the astral charm). I found that he had 45 HP by hitting him with uncharged arrows (my "1 damage" attack) and based the rest of my values on those findings. After that it was just a matter of hitting him with an attack and then counting the number of uncharged arrows it took to finish him. Subtracting that number from 45 gave me my damage value. I repeated this with every item and weapon, and with differing loadouts of passive items to see which attacks could benefit from damage boosts.

Maple Leaf (Red Leaf)
Your basic weapon. Moves consist of a 3-hit combo and a single hit jumping/aerial attack.
Damage:
1st hit: 1
2nd hit: 2
3rd hit: 3
Jump attack: 2

Fresh Spring Leaf (Green Leaf)
Same as the red leaf, but does more damage.
Damage:
1st hit: 2
2nd hit: 3
3rd hit: 4
Jump attack: 3

Arrows
Your basic ranged weapon.
Damage:
Uncharged: 1
Level 1 charge: 2
Level 2 charge: 2 per arrow
Level 3 charge: 4 per arrow

This is a list of all the damage dealing items in the game. Items that grant you buffs will be in the next section.

Blessing Charm
Summons 8 projectiles that slowly orbit your character in a circle pattern.
Damage: 2 per projectile

Bloodstained Tissue
Summons 8 projectiles that swirl around your character in a spiral pattern that quickly widens.
Damage: 4 per projectile

Violet Sprite
Summons 4 projectiles that orbit your character in an oval pattern.
Damage: 1 per projectile

Sealed Wind
Summons a gale of leaves at your location. Cannot hit the same enemy more than once. Lasts for 5 seconds.
Damage: 6

Sparse Thread
Releases a small explosion around your character in a circle pattern.
Damage: 20

Bakman Patch
Causes 104 bakman to rain down from the sky in front of your character.
Damage: 0.25 per bakman

Edea's Pearl/Dull Pearl
Causes your arrows to poison foes. Poison effect lasts roughly 13 seconds.
Damage: 11 (not counting any damage from the arrow itself)

This section will list all of the items that grant you buffs/damage boosts. "Weapon damage" refers exclusively to damage dealt by the leaf or the bow.

Heavy Arrows:
Gives a 100% boost to arrow damage.
Makes arrows slightly larger.

Pocket Incensory:
Adds 0.5 damage to all attacks, including active items.
Allows you to stagger enemies easier.
The damage boost from this item is not affected by % damage boosts.

Black Sachet:
Gives a 50% boost to weapon damage.
Has a 6.66% chance to hurt you when you attack. Damage dealt is equal to 10% of your max HP. This damage can still occur from using an active item, though it will not receive any damage boost.

Crystal Seed:
Gives a 50% boost to weapon damage.
Lasts 15 seconds.

Tainted Missive:
Gives a 100% boost to weapon damage.
Damages user upon activation.
Lasts 15 seconds.

Necklace of Sacrifice:
Gives a 100% boost to weapon damage.
Only works if you are under 25% HP.

Notes about stacking:
There are two things you need to know about stacking in this game. The first is that active items do not stack with each other. That means you can't use Crystal Seed and Tainted Missive at the same time. Everything else is fair game.

The second thing you need to know is that damage boosts in this game stack multiplicatively. This means that every boost grants you bonus damage based on your current total damage, not your base damage.

For example: A jumping attack with the green leaf does 3 damage. Black Sachet gives a 50% bonus so we go up to 4.5 damage. Now, adding in a Necklace of Sacrifice gives us a 100% bonus, but this is applied to the 4.5 (total damage), not the 3 (base damage). So we end up at 9 damage instead of 7.5. Adding in a Tainted Missive at this point puts us at a massive 18 damage becuase it boosts us by 100% again.

With multiplicative stacking we are in reality receiving a 500% damage boost (3 to 18), whereas an additive stacking formula would give us a 250% boost which would put us at 10.5 damage.