Densetsu no Starfy eraser
From Starfy Wiki
Not to be confused with the Game Boy Advance cartridge erasers
The Densetsu no Starfy eraser is an eraser based on Densetsu no Starfy that comes in a packet with the box-art of the game. It was produced by Showa Note. It was sold on November 20, 2002 for 100 yen (excluding tax). It is now discontinued.
This was one of various official merchandise used to promote Densetsu no Starfy as listed on the official mini-site's Goods section.