This story is... nonsense.
The beginning seems good - kidnapping, ransom, abandoned school. However, then... The only one thread is ok, which concerns Mitsuru and his sister. Unfortunately, the spectre-school girl is totally misses. There is nothing explained and these scenes look like fragments from other film. I would like to know causes of death of these guys... Sorry, but the girl from ransom is real or it is only a spook... I know that there is the sister's soul, but then perhaps, the souls disappears...? I don't know. It's not difficult to watch the film, but how to understand it then... oO