You can "Marry" another Character. This will provide additional passive Effects by increasing your Couple-Level. Your Couple-Level gains EXP passively if both Characters are Online at the same Time. The Effects only Apply on certain Couple-Levels and if both Characters are Online.

Open with F by default

Couple-LVL	Buffs (Name + LVL)	Effect
1	-	-
6	Power of Love (1)	Increases Attack Power 1% and Increases HP 1%
11	Power of Love (2) Blessing of Love (1)	Increases Attack Power 4% and Increases HP 4% Increases Speed by 5% and PVE by 2%
16	Power of Love (3) Blessing of Love (1)	Increases Attack Power 7% and Increases HP 7% Increases Speed by 5% and PVE by 2%
21 (Max.)	Power of Love (4) Blessing of Love (2) Miracle of Love	Increases Attack Power 10% and Increases HP 10% Increases Speed by 10% and PVE by 5% Increases Item Drop Rate from monsters by 50%