Max Mana?

Is there any way to increase your max mana? I know there probably isn’t, but I figured I should ask anyways. I was really enjoying the main story, but then it shifted to the online story and quickly became much too expensive. 4 battles is basically 150 mana out of a 300 max, and it’s crazy. On top of all this, it just doesn’t regenerate fast enough. Maybe I’m just impatient, but I really think that this is just crazy. I still really enjoy the story, I just want to play a bit more in a single day.

Mana increases with your hero rank. Forgive me but I can’t remember the max. I agree that you can’t do many story battles each day with your mana, it’s a shame