Hanayama Starfish - Cast Metal Puzzle

In the summer of 1997, I saw two mackerels that had somehow managed to get into the sardine tank at the aquarium. Watching these two fish unable to blend in with the shoal of sardines made me wonder if they were on a journey of self-discovery.
What sort of adventure will they have?
Imagining this led to the conception of six cast puzzles based on oceanographic subjects.
Subject: Starfish
Two mackerels jostling for a starfish. Separate the starfish from them, and then put them back together.

- Yamamoto 2008 -