Once you reach a new level your experience returns to 0.

Character Experience

(each may only be attained once per battle)
Defeated Lesser Skilled Opponent  50
Defeated Equal Skilled Opponent  100
Defeated Stronger Skilled Opponent  150
Defeated Lesser Numbers   50
Defeated Equal Numbers   100
Defeated Superior Numbers   150
Inventive Fighting    50
Protected Ally     50
(each may only be attained once per game session)
In Character For Entire Game Session 300
In Character For 75% of Game Session 200
In Character For 60% of Game Session 100

Character Experience Needed to Reach New Levels

LVLs 2-5 2, 000 each
LVLs 6-10 4, 000 each
LVLs 11-15 8, 000 each
LVLs 16-20 16,000 each

Newtype Experience

(each may only be attained once per battle)
Defeated Lesser Skilled Opponent  50
Defeated Equal Skilled Opponent  100
Defeated Stronger Skilled Opponent  150
Defeated Lesser Numbers   50
Defeated Equal Numbers   100
Defeated Superior Numbers   150
Battle Newtype Rival    50
Newtype Rival Survived Battle  50
Protected Newtype Ally   50
Newtype Soul Mate Present During Battle 50

Newtype Experience Needed To Reach New Levels

LVLs 2-5 2, 500 each
LVLs 6-10 5, 000 each
LVLs 11-15 10, 000 each