Minho
Plant spirit; can both turn into a plant and control actual plants. Likes to chill out as a Mangrove tree or pretty flowers. Has lived (alone) on the island for an undeterminedly long time. Likes that Jonghyun lives with him now and that Jinki/Kibum/Taemin visit often. 

Jinki
Water spirit; can control the ocean and breathe underwater. Has a somewhat non-corporeal water form but mostly stays in person form (he got tired of being bumped into). Claims to live at the bottom of the ocean but spends most of his time around this island. Likes to go treasure hunting with Taemin. 

Taemin
Storm spirit; can call up rain, lightning, and clouds as he pleases. He lives in a cloud cave with Kibum. Likes to visit Minho&Jonghyun's island to somewhat literally rain on their parade. Also likes to go treasure hunting and make unnecessarily large waves with Jinki. 

Kibum
Wind spirit; can control the wind and rides it around. Lives in the clouds with Taemin. Likes to play on Minho&Jonghyun's island. Likes to send strong cold winds at the island at the exact moment tree!Minho has gotten all set up and comfortable, just to ruffle his leaves. 

Jonghyun
Animal "guardian"/spirit; is supposed to protect other animals from stuff, but since he lives on the mostly uninhabited island with Minho, he just spends his time turning into animals as he pleases. Likes to be a puppy and play around with Minho, especially if it means bothering Kibum.