Now to the point: hammerbug – and anybody else reading this – I don’t want to come off sounding like a Internet troll, but PLEASE tell me you’re kidding. You’re how old, and you’re telling everyone on this forum that you don’t know a cleavage line when you see one?
As far as fans of the original Yugi-Oh are concerned, Mai clearly uses her, ahem, "assets" to distract her opponent during a duel – the viewers oughta be lucky that this little piece of fanservice got past the network censors!
Where cartoon character designs are concerned, don’t over-think it – you’ll only give yourself a headache.