Actually i think it will be the other way around.
Asami has to fall into the Abyss of fearing he lost Akihito to admit all of his mistakes and shortcomings and become a better person.
Asami fell in love with Akihito because Akihito "lives in the world of light" and is not a part of Asami's underworld. If Akihito now became a part of the underworld he would cease to have THAT appeal to Asami - and it would be a character-rewriting that would make the Akihito we once knew come to an end.
And especially that last part I do not see. In terms of writing Akihito is to remain the everyman, the one we can easiest identify with, the one which withstands everything and remains true to himself
He can't become a part of the underworld, but it will be Asami who will have to save him finally to protect and to shield him of that world.
I prefer Sakazaki x Sudou instead of a dragging AxA which had already became boring as fuck.
Not saying fanfics are bad, but there are a ton of fanfics where there's memory loss (usually Asami) or badass Aki.
I feel like this might be important to the whole entire Aki falling into the abyss with Asami thing. He has to be broken first to get the skills necessary to survive the underworld. The easiest way to explain getting good in a short amount of time is amnesia + brainwash.
Then Asami will try to help Aki recover his memories by recreating sexual encounters, and creating doubts in Aki about his current "truth". Sort of like, "Your brain can forget, but Your body remembers. " type thing. Then they'll finally take down Sudouzaki. Man, they're annoying as fuck.