What's actually eaten is the urchin's gonads, not its flesh — five bright orange tongues inside a shell that's otherwise almost entirely spine and water.
The spiky kina shell is cracked open to reveal its bright orange roe, scooped out and eaten raw with a spoon, straight off the rocks or spread on bread. Along the Bay of Plenty coast it's gathered by hand at low tide and shared straight from the shell rather than sold in shops.