This is simply a Manga about a woman who doesn't want to cheat on her husband because she wants to be a true and faithful wife. Husband doesn't care for sex and leaves wife unfulfilled in both spirit and physical needs.
She can see the supernatural and often avoids them, the supernatural don't like to witness awkward stuff but they do like attention.
She is having s** with her husband when a ghost looks at them and keeps watching...
To skip to the point the ghost gets stronger as she engages in s**ual fantasy's with this ghost as cheating with a ghost isn't cheating. The ghosts gets powerful from absorbing her vitality but she just works out more and eats more to keep providing.
The husband is a terrible person and the wife is an equally terrible person. The husband just wants to look normal, is very bland and just wants to be married to have somebody cook him food and clean the house, he wants kids supposedly but doesn't want to care for them.
The wife stays in a no-existant relationship. She knows that there is no love and that there will be none but still stays in the relationship that gives her nothing.
The ghost is selfish because it's a darn ghost, it's dead and wants everything it doesn't have.
I'm on chapter 7 so far and I hate everybody, the husband and wife, the wife's friend, the ghost, and the stupid ghost whisperer dude.