You will need a standard Game Boy Advance emulator capable of reading ROMs.
In Granbo , players take on the role of a "Granbo Saber," a trainer who collects and battles robotic creatures modeled after real-world animals. Granbo Gba English Version
You're referring to the English version of the popular Japanese visual novel and adventure game "Granblue Fantasy" (known as "Granbo Gba" in some regions). You will need a standard Game Boy Advance