If you like resolution in the stories that you read, then this will likely interest you. I have never read a story with such a mysterious beginning and open ended vibe that has been able to conclude in a satisfying ending that answers pretty much every question that you could have about it. The author does a splendid job at tying everything together and while things do remain a mystery during the events of the story, everything is made to fit like a puzzle and makes complete sense in the end. The storytelling is wonderful, and I just couldn't help but read the whole series in one sitting.
「Companion」or「Tsurebito」is not only a marvelous example of storytelling, but also a journey through life and death, fair and unfair, from many perspectives; truly making it a thought provoking read. I do hope you will choose to give it a read.