It seems like the mangaka lost motivation for this and just rushed to the ending. I was anticipating Sumi managing to get the company back, but that abruptly ended. Started off good, middle got bland, and ending was horribly rushed
Maybe you just had higher expectations and saw more potential in a different ending, but there aren't really any loose ends. Or maybe you wish it would have drawn out longer and taken time developing, in which case I remind you this manga was fast-paced and compact with drama from the beginning. A big twist doesn't necessarily mean rushed to finish.
I'm an idiot
I just kept reading and I was so confused and then after I finished, I finally realized (thanks to all the comments) that half of the story was missing