Amusing. Instead of asking questions like "how big boob gotta be for female to be adult" like a simpleton, ask instead why the age of consent exists in the first place, and why people object to depictions of minors in sexual activities.
Age of consent isn't about looks, it's about making sure people are of an age where they understand what they are getting into, that they are mentally matured enough to do it, and also mentally mature enough not to be taken advantage of by predators.
Your absolutely amazing, deeply thought out questions about "what if woman too short to look adult" or "what if woman has no boob" are nothing more but empty sophistries. But since you are committed to using the mental capacity of a monkey when making these snide remarks, allow me to make it as clear as possible where the point of discontent is when it comes to pornographic artwork of children.
When you go to jack off to your hentai sites and look up loli and shota shit, it doesn't matter when the character is a billion year old dragoness looking like a 7 year old. Likewise, in most porn where it's got young looking actors, the actual age of the actors involved, for the context of what you are watching, doesn't matter, because the intent is to get your peepee hard at the fantasy being sold. People won't jack off to the dragoness' personality, they will jack off to her childlike body. Likewise with the porn.