The levelling system in Blue Reflection is called Status and is broken down into Growth Points, Parameters, Attributes and Ether Skills. These are based on points per stat per level. The level cap for the playable characters is level 50.
Some actions like Fragment stabilization, will reward you with Growth Points for your Reflectors. Using a point to influence a characters stat growth will cause her to level up.

Playable Characters refers to: Shirai Hinako, Shijō Yuzuki, Shijō Raimu.

Character Levelling

Growth Points

You can grow the main characters under "STATUS" by distributing points you receive from completing missions or events. When a certain amount is reached, you will learn a new Ether Skill.
Attack - Increase Attack
Defense - Increase HP & Defense
Support - Increase MP & Luck
Technic - Increase Agility

Each level up has a minimum stat increase value per level regardless of which Growth Point is chosen.
Each one of these four Growth Points is associated with either one or two stats (as explained above) and in addition to the base stat increase, the chosen option will further increase the associated stat(s) in the following manner:

If the value of the option after spending the growth point is:
8 or less: +3 points
Between 9 and 22: +2 points
23 or more: +1 point

Parameters

Level (Lv.) - The current level of each character. Distributing growth points to a character will increase their level.
Hit Points (HP) - Characters will be unable to fight, if this number reaches zero.
Mana Points (MP) - MP is depleted as you use Skills.
Attack (ATK) - The higher this number, the more damage you can do to opponents. Equipped fragments can change the effect of your attacks.
Defense (DEF) - The higher this number, the less damage you will receive from opponents.
Speed (SPD) - Affects the order of performing an action, chance of evasion, and ability to successfully escape.
Luck (LUK) - Affects critical hit chance and evasion chance.
Attribute - Each Attribute: Slash, Heart, Impact and Pierce have strong and weak counterparts.

Attributes

There are four (4) types of attack attributes linked to Parameters and Ether Skills:
Slash, Impact, Pierce and Heart.
Using the attributes an enemy is weak against will deal higher damage to them. But if you attack with an attribute that an enemy is resistant to, you won't be able to deal them much damage.

Double Circle: Weak - Large (Very Strong against enemies)
Circle: Weak - Small (Strong against enemies)
Line: Normal (Average against enemies)
Triangle: Resist - Small (Weak against enemies)
Letter X: Resist - Large (Very weak against enemies)

Ether Skills

You can learn new Ether Skills by using Growth Points to meet each skills stat requirements. Focusing on Attack will yield more offensive skills. Defense will yield healing and protective skills. Support will allow you to buff your allies, and Technic will result in unique skills that defy categorization.

Advanced Stat Values

A full list of stat values is available for Hinako, Yuzu & Lime.