Red pearl
From Starfy Wiki
Red Pearls are five special Pearls in The Legendary Starfy. They only appear as items in Gluglug Lagoon, (Stage 1-2) as part of the "Herman's Red Pearls" Side Quest, in which Starfy must find them for Herman.
In the Side Quest Herman says that they are "super-rare". If Herbert doesn't find them, he "can't buy the good treats" ("high-class fishie food") for his Coddies. He insists that his Coddies "can't eat just regular snacks" because it would be "cruelty to Coddies".
After Starfy helps Herman find his 5 Red Pearls, Herman grants the player access to Gluglug Lagoon's Area Secret 1.