These events are appearing periodically, such as Lucky Wheel, Sub-space, Monthly Carnival and Gem spending events.
Lucky Wheel
You can use Spin Coins to spin the Lucky Wheel. The Lucky Wheel appears at the top of the right side screen on the Main Page. Each month the Lucky Wheel features a different girl to give the opportunity to each player to level up the character they desire.
Sub-space
The Sub-space event can be located on the Main Page near the Upper Right Hand side of the screen. It is marked with a Swirling Purple Portal. In this event you clear 18 story stages and 3 Boss stages in order to receive rewards.
Also, certain characters will be boosted to provide extra Attack, Recovery and HP. The story stages will drop Sub-Space Boss Tickets. The Boss stages require Sub-Space Boss Tickets in order to access them. These stages drop the actual rewards and Exchange Tokens.
Take into account that Sub-space Boss Tickets and Exchange Tokens will reset after the event is over.
Monthly Carnival
Complete tasks in order to receive Carnival Token. Collect the tokens in order to exchange for the rewards. The Carnival is the only event where you can gain Memory Fragments for girls like Giselle and Mina.
Take into account that Carnival Token will reset after the event is over.
Gem spending event
During this event you will spend Gems and receive rewards. You can collect the rewards in the Bonus area of the game.