Well that's the thing about art, it doesn't have to be entirely realistic. Like when I draw and sketch I have a habit of giving the women hour glass figures which I know isn't realistic but hey its art, you shouldn't be confined by the laws of society. If it was actually made to be realistic it would've been boring, especially considering DOA5's female models are fare from realistic, especially Honoka who has a 99 cm chest and ass and short hands all on a short frame like hers....that's not realistic at all and no artist could avoid not making her the way she's designed, same with Ayane.
That is the thing you failed to understand, DOA bodies are actually really well structured if we go by human body and how it works, breasts are soft, they don't float, they are not round, they position themselves in a very good way, same for the rest of the body, is actually decent reference material if you want to, is about making the body look natural and soft, and this comes with a very deep study myself, to not go too off topic, you can private message me, since art in general is one of my favorite subjects and i can explain some points and also give you some reference.
Now to post some DOA fanart that will also serve as reference to what i'm trying to say and to keep on topic.
source
You can see that Tina still have massive breasts here, but they're affected by gravity and her top.
Also here.
source
In both pics you can see, really big breasts in general, sexy ladies, but with fidelity to how the human body works to a greater extend, it makes everything more soft, more natural looking and sexyer as well.