So we get to see that Ichigos mother was to be married to carry on the pure blood Quincy line. This is obviously nothing she wants but she is by far too nice to say no.
So how did she get out of this?
My theory is the, Quincy Letzt Stil. I think she had a Sanrei glove and use this.
It is described as a double edged sword and could have been used to in some way help Isshin out with the Vasto Lorde.
If this is true then she squishes 2 flies in one swift stroke. Loses the Quincy powers just like Ishida did in the SS invasion arc and saves Isshin. No more marrige, one dead VL and eventually a happy family.
No because its already been shown its quite possible to recover your powers. Even the man who was able to do it was engaged to her plus his Faja ,Soken probably taught him and he's obviously still alive as well. As for the fight I can't even guess. When the flashback started it kinda showed the end of the fight and she looked completely fine and even offered to heal him. So either shes l33t or she caught the hollow when he wasn't looking.
My guess is the same (Letzt Stil) or perhaps she even had Vollständig. Or some other technique that's effective against Hollows. Maybe Sklaverei?
I don't think you would use the Sanrei Gloves to save a stranger from an attack. That looks too much of a stretch. You'd probably rather see them get killed, since using it would potentially mean you wouldn't be able to save anyone else in the future.
^Masaki has been made out to be a very warm empathetic person, so it could be that she used it.
I'm positive that this fight is going to end with that hollow being absorbed or sealed inside of her. It's the same mask as the last hollow transformation Ichigo took so without a doubt her reistu will be tainted and pasted down to Ichigo. Also keep in mind that Isshin is going to be using FGT too and being losing his power. But it would be pretty intense to let out that kind of power in a town.
But as for Isshin, i also had the thought that he lost his powers due to usin FGT, but there is also more then one way to lose your raiatsu, and that' to use the gigai that Urahara made. The same one that he gave to Rukia at the start of this whole manga. It saps the raiatsu from your body to the point you don't even become a shinigami anymore. I think that's how he really did it. He fell in lov with her and decided to get rid of all his raiatsu to be with her.
If i'm not mistaken, Urahara's objective would be to get rid of Rukia's raiatsu and shewould have become human. Isshin probably wanted to become human so that he could live a happy life with the love of his life. Shed his entire shinigami self.