Nameko

[Thalon]

I aquired those mushrooms but I can't do anything with them: the walktrhough says they're consumables that increase the attack power, but when I try to consume them I recieve a weird message like "I can't store any more".
Is that a bug?

[Don Rumata En Regalia]

They add charge combo uses to the meter, letting you use more advanced combo attacks (mainly the ones that hit everything on-screen). So when your meter's full, you can't consume any more shrooms.