Precious necklace from an angel

A broken heart girl , read her diary when she was in high school , the boy she loves die while protecting her , he confesses to her at that moment and gives her a necklace saying he will be with her and protect her while putting it .
She had been upset since that day , but she met a boy who will help her to smile , yes to smile .
But this boy is an angel , this angel is Kai the boy who died , he came to this life with another face to do a mission , and it's make her smile again .
What will happen after ? Will she recognize him ? Will she fell in love with him ? And will him stay her ?

part one the book : diary ( tlking about the person cause that her this sadness , the persons she loves and hates )
part 2 : living every single day with the girl , every thought and the most impotant what she feel , love , sadness ...