I really never expected such a dramatic plot twist. o_o I really liked the fluffy, slice-of-life type beginning, but that plot twist makes it all better...
It does get confusing, but I highly suggest plowing through it and then thinking about the plot. The whole setting of the manga is based on irony. The selfless, nice person is actually a selfish, mean person. The selfish, mean person is actually a selfless, nice person. It's set in a world where people can't die yet at the same time die, so you'd have to expect this much. Just don't base your judgement on first impressions of characters but rather what the characters prove themselves to be. For instance, Hampnie can be subject to much criticism because of his actions, but if you read on, you'll find that your first impressions of him will be changed. [For better or for worse, I guess that's up to you.] Ai's adoptive family may seem caring and loving, but if you pay attention to the details, they'll prove to be different. [Likewise, for better or worse, it's up to you.]
From what I've read, Hampnie killed Ai's adoptive parents because they were bad people who were forcing Ai into the life of Gravekeeping. Gravekeeping is a despicable career, but Ai doesn't know that. In order to protect Ai from this lifestyle, Hampnie killed off everyone in Ai's village. If you look closely, the villagers despised Ai and only pretended to care for her. Hampnie, on the other hand, pretended to despise Ai but actually cares for her. Hampnie's character is pretty tricky, because he puts up a mean, oppressive, and almost evil demeanor but cares for others. This is probably because of the fact that he has the ability to come to life again after death, but that part's just a speculation.
Ai plays a crucial role as the normal, sane observer who views everything in the point of view of a normal person who is thrown into a world of abnormality. [Though it's ironic that she's actually an abnormal person, but that's besides the point.] If you focus on her observations and think in her point of view, things should click into place. After all, we are normal readers who are reading about an abnormal world, just like she is a normal character living in an abnormal world.
tl;dr
Don't read everything in a 2 dimentional, straight forward way. Don't cast your judgements too early. Remember that everything is ironic in this story.
But congratulations on getting an anime, Kamisama no Inai Nichiyoubi! You really deserve it uwu