Absence Makes the Heart
"Absence Makes the Heart" is an 'The Island Mystery' quest this related to the 
Island Spirit. The quest is unlocked after the player has completed the "Friendship Never Fades" quest series.
Quest Description
"Find out how to help the Spirit of Friendship Island"
Quest Information
The player must speak to 
Badtz-maru, who explains that his friend, 
Keroppi is feeling down due to worrying about the Island Spirit. Badtz-maru will then tell the player to go gift Keroppi a snack, which can be any cookable item the player has in their inventory. After gifting him a snack, Keroppi will continue to brainstorm ways to cheer up the Island Spirit before the player suggests giving the Island Spirit some more 
Spirit Hearts. Keroppi likes that idea and the player must then bring a 
Best Friend to the 
Heart of the Island — in order to do this, the player must have reached maximum friendship with the Island Resident, indicated by a golden heart, and the Island Resident must be able to be the player's companion.
Once the player has one of their best friends as a companion, they must then travel to Heart of the Island, and speak to the Island Spirit. She'll greet the player. Suddenly, a heart will appear between the player's best friend and the player. It will spin quickly until turning yellow and float towards the 
Island Spirit. The large heart that she is inside will glow a strong light, before becoming less dark. Island Spirit will then explain that they're tired and that she will see the player again soon. Afterwards, the player must speak to Keroppi, who is at the end of the 
Gemstone Mountain dock.
