Getting a feeling that we will find out more about Yumenashi-sensei in the next story ark. Shogi and piano are both things you can be immensely talented at but not able to break into the level where you can earn a living doing it.
A large part is the mystery. If it had just been a weird power fantasy were a guy wakes up, is super hot, and can read the minds of women it would have been a easy drop. The first person perspective and the fact that the protagonist is trying to figure out what all the interface stuff means...
I imagine the killing of the pregnant seal is supposed to be symbolic of sacrificing the future for the sake of the present. This goes along with the eating of the potato seeds, there is no future for the island regardless of the outcome now.
Everything in most media is usually exaggerated but I would suspect maybe in this case not as much as we'd except. Think about it in terms of religion, Buddhism doesn't disallow ghosts or spirits, Shintoism heavily involves them. Consider how many hard core religious people are around you and...