I don't understand why the history finished so fast. This manga gave me the impression that there were a lot of points to develop but most of them got lost. For example, what was all that about Niina going to a University if in the end she got married so fast?
After Niina's childhood it seems like the plot was not well structured. BTW, I even thought they could have developped more Niina's childhood side. She seemed so strong and sure of herself in the first moment, even more than the adults around her because she had past memories. Although, when she became a High School student I feel her personality a bit strange; she was not a weak girl but she didn't have the strong presence she had before. What about that high school boy that used to love her, btw? The last chapitres were really strange. It seems like the manga must be finished quickly, so a lot of events happened in the same time and some of them were forgotten: Get father's permission, finish high school, get married and go to University and we saw all of those things super fast - like what the hell happened to the high school boy who has confessed to her?
The history started really nice specially with that reincarnation atmosphere but even it has finished in a freak way. I think some points they should develop were put aside or just finished too fast.