>>57317007May is based on the female player character from the third gen of games. To create a, mostly illusory, sense that the games were progressing somewhere instead of being barely changed minor iterations of the first game, the player characters were said to be 12 years old unlike the 10 year old player character from the first game.
To differentiate a 12 year old girl from a 10 year old one the artist gave the female player character small but extant breasts as she has begun puberty.
When the character was put into the second series of anime, her age was reduced to 10 to match the protagonist from the first series who becomes her companion; if she was older it would seem awkward for her to learn things from someone younger than herself (this would be more important to a Japanese audience).
But now she's a 10-year-old with small but extant breasts that were meant to make her DIFFERENT from a 10-year-old. She is now busty for her age. The animators had fun with it from there, often making her much bustier than she is in her original art for the game.
