The Hirotta Stone (ヒロッタストーン) is a symbolic stone presented to Alex Kidd in exchange for the Personal Letter to the Kingdom of Nibana at the Kingdom of Nibana. The stone contains the key to finding the Gold Crown.
On rescuing his brother, Egle, Alex is informed of a letter to the Kingdom of Nibana present in Radaxian Castle. Alex proceeds to the Nibana Kingdom in possession of the letter to the King of Nibana to acquire the Moonlight Stone Medallion. However, by the time Alex reaches the kingdom, the medallion has been stolen by Janken the Great. Instead, the King of Nibana, High Stone, gives Alex the Hirotta Stone and sends him in the direction of Cragg Lake to find the Gold Crown.
The meaning of the inscription on the stone does not appear obvious immediately. However, once Alex reaches the crown room at the bottom of Cragg Lake, its use becomes more apparent:
Reading from top to bottom, right to left, the symbols read:
This is the order in which the symbols must be activated to unlock the Gold Crown.
If Alex had not acquired the Personal Letter from the Radaxian Castle, he cannot get the Hirotta Stone. The King of Nibana will dismiss Alex and summon a ghost to kill him unless Alex ends the level.