I am hoping desperately that this manga returns from hiatus soon.
The manga handles the easily convoluted concept of reincarnation with deftness and humor that many other series fail to do.
Unlike NG Life, a rather similar manga (which I actually did not like much), where the emphasis seemed to be that reincarnations are in the end now different people and should be viewed that way, Yukarism's view is that even if they have no memory of the past, their soul is the same and therefore they remain the same even if they have changed appearances.
To quote one of the characters: "It's amazing how much a person's tastes, thoughts, and life path are similar as their previous life."
This is proven to be very true, and most certainly with Yukari. Some people might be annoyed with Yukari's detachment and "cool guy" personality but this is a direct reflection of Yuumurasaki, who, despite her smiling exterior, was empty inside due to the harsh world of the red light district.
Mahoro is the same as well. She displays the most differences due to having lived as an ordinary girl - being a girl, particularly that of the usual, regular family, means she would have absorbed society norms of what a girl acts like - but her core personality remains very similar to her past self.
Considering Mahoro's past life,
I think it would be very interesting if in the end, Mahoro will be the only one to remember the past. Takamura said he is an outlier, so likely Mahoro is the same as well. Souls don't change, after all. Most likely, all of them would forget the past, but I do hope the mangaka would forgo such an obvious ending. (Hopefully this is one of those series where they -don't- forget once remembered. Takamura/Mahoro's ability to cast spells is very cool and it'd be a damn shame to get rid of it. Haha)