Neither, really. She started out as a company mascot, first used for a music festival, but proved popular, so the company that runs the festival expanded her into a media franchise.
A media franchise where this really has nothing to do with her boobs but really is just all about her boobs. XD
Let's see, for example:
Everyone on the beach is obsessed with her boobs.
Sempai is blindfolded on a beach and somehow just accidentally puts his hands up her bikini top to unknowingly fondle boob without knowing what it was.
Sempai accidentally feels her up while using virtual reality.
Sempai freaks out over her boobs shaking on the massagers and work out equipment and tries to take her out of the store.
Sempai unknowingly snuggles his face in her boobs while sleeping.
Sempai is happy not being able to see anything on her lap because the boobs are covering his face..
That is all this is about. Now I wish people would stop talking about this WEEB crap so I won't be made to go watch it just to see WTH they are going on about.
OT: I don't have a problem with the depiction of her body type. I am large breasted with a small waist so I relate to that, however, I have a problem with them portraying people as stupid and kidlike in sexual situations which that is the entire theme of this show and numerous others. Like it is not somehow going to be sexual for two college students to be all over each other like this, like when she is digging in the bushes for the cat with her exposed panties out and he just happens to have her by the waist pounding her from behind but it wasn't sexual and the guy was somehow mortified for people thinking it was ? YEAAA. no one on the planet is THAT stupid. In RL the guy would be the Eiffel tower and no way he wouldn't be thinking about that in any of the real situations so the entire theme and premise of this show is just idiotic to begin with and caters to people attracted to child like qualities.