[quote=@Blu]
<Snipped quote by Pyromania99>

Hmm... Has Naoto's bust always been that noticeable. I never played any of the P4 side games.
[/quote]

[quote=@GreenGoat]
Nah, she always had a rather small bust. 
[/quote]

Nope, It was implied she was rather big.  When Naoto first joins they go to the hospital for check ups right? Rise looks at Naoto's report and freaks out.  From some of the wording it was implied she was larger. Then there is the afterstory part of Golden where she is outright shown like that I believe.