Checkpoints, are the "Magic Challenges" required in order to proceed in the stories. There are two types of Checkpoints: "Avatar Item" and "Magic Grade".
Avatar Item Checkpoints[]
In the main stories routes, the first avatar item requested will always be a normal item, while the following ones will give players the chance to choose between normal or premium items.
According with the game Currency System, normal items can be brought with both Lune and Coins while the premium ones can only be with Coins.
Magic Grade Checkpoints[]
Each route in the game has eight Magic Grade checkpoints, in which your magic grade needs to meet or surpass a given requirement before you are allowed to proceed with the story. Note that Magic Grade is reset from 0 each time a route is started (although the game does keep an internal tally of your accumulated Magic Grade across all play throughts).
The Magic Grade can be increased by participating in Extra Curriculum or with Consumable Items.
First Challenge - 500 magic grade
Second Challenge - 2000 magic grade
Third Challenge - 4000 magic grade
Fourth challenge - 7000 magic grade
Fifth Challenge - 9500 magic grade
Sixth Challenge - 11250 magic grade
Seventh Challenge - 14500 magic grade
Eighth Challenge - 17000 magic grade