Moves that don't knockdown are usually cancelable into other moves, jumps or dashes. The first, and to a lesser extent the second and latter, are what makes comboing possible. The idea of combos in this game is generally to link various moves that don't knockdown, and then a combo finisher that does knockdown, which is many times a super, due to their higher damage output.
Combo Breakers
If the player who's getting hit has enough meter, they can press O to do a combo breaker, which spends one meter bar and 100% of the stamina bar. It is not possible to combo break grabs, guard breakers and supers. There are two types of combo breaker, depending on which series the character is from:
Burst: characters from Bleach and Kenshin cause an explosion when they combo break
Pros: guaranteed safety, yellow armor
Cons: low damage
Substitution: characters from Naruto teleport forward with no hitbox
Pros: can be used to get a grab or other combo starter
Cons: riskier, has no armor, can sometimes be trapped by big hitboxes or even punished by ghost step
Meter is used on only two actions: supers and ghost steps.
I/WI/KI - 1 bar
SI - 3 bars
SL/WL - 60% of a bar
Stamina is used by various dashing, ghost stepping, combo breaking and shielding moves. You can do actions that require stamina even if you have 0 stamina, but if you go below 0 it'll take a lot longer to recharge.
L - 20%
KL - 30%
SL/WL - 80%
Combo Breaker - 100%
Shield and armor spend stamina relatively to the strength of what they block
Shield only blocks attacks that come from the front, but the player is free to turn around while in shield. Blocking moves spends 1 stamina for each 5 damage blocked (full shield has 500 HP), and if there's no stamina left to spend, the shield breaks, leaving the character stunned fow a while, and unable to combo break if the opponent hits them.
Grabs and Shield Breakers
There are two properties of moves designed specially to beat shields:
Grab - goes through shield; besides the normal grabs every character has, some also have command grabs, moves with the grab property, signaled by the purple spark
Shield Breaker - doesn't go through shield but does extra shield damage; usually very slow; shield breakers that don't knockdown make it impossible for the opponent to combo break
Armor
Armor is the property that allows a character to go through attacks, while reducing damage taken, but spends stamina relatively to the strength of the armored hit. There are two kinds of armor:
White Armor - reduces 35% of the damage; can't armor if the character has no stamina; can't armor grabs and supers; present in many attacks and a few supers
Yellow Armor - reduces 70% of the damage; can armor even with no stamina; can even armor grabs and supers; present only in burst combo breakers and a few supers
Dashing is one of the most important movement options in this game. All dashes have frame 1 invulnerability and spends 20% meter on the ground and 30% in the air, but the dash distance, speed and endlag vary between characters. It is only possible to dash once while airborne, but multiple dashes can be used in succession on the ground. Dashes can be canceled into some supers, and a few characters can cancel dash into normal attack, which is called a dash attack.
A grab is executed by running into the opponent and attacking. Blocking is a frame 1 option that goes through shield, makes it impossible to combo break and has little endlag on whiff. There are two kinds of grab:
Normal Grab - does 50 damage and starts combos; executed with normal attack
Special Grab - does 150 damage and does knockdown, making it vitually useless when not accidental and should be canceled into a ghost step after the purple spark on reaction to start a combo; executed with special attack
Ghost stepping is the single most important mechanic in this game. It spends 60% of a meter bar and 80% of the stamina bar. Ghost steps are key to all states of the game, being an universal combo extender in advantage state, a mean of reactionary safety in neutral and a powerful way to escape pressure, setups and juggles in disadvantage.
Ghost Jump and Ghost Drop
Besides the usual ghost step that goes forward on the ground, there are two other possible directions to ghost step
Ghost Jump - WL - goes up
Ghost Drop - SL - goes down - can only be executed in the air - canceled by landing