FFX - Sidequests - Butterfly Catcher
In Macalania Woods talk to the strange creature. Move toward the closest butterfly to begin the game. You have to chase down seven blue butterflies before the time runs out and avoid the red ones; if you hit a red one a battle starts and you lose one second. If you manage to capture seven butterflies a treasure chest will appear. Claim your prize before you leave the area or else the chest will disappear.You can play the game in one of two areas: Macalania Woods North and Macalania Woods Central.
As the story progresses the mini-game get harder. As soon as you encounter the Macalania Woods the time is 40 sec. After you beat Spherimorph the time is lowered to 30 sec. After you gain control of the airship the amount of red butterflies increases.
If you beat the mini-game in both areas you will get the Saturn Sigil to power-up Kimahri's legendary weapon.