I think the mother x daughter relationship is one thing (consenting adults! That's fine! Nobody's business!)
But I think having a sexual relations with a minor is another. I guess, if I am alright with it in a manga, then my justifications for it not being alright in real life would be thinned a little. So I do hope Ayako waits until later to get on with Akira.
(Pardon me for mistakes, English is my 2nd language!)