Wings of the Unknown

Ricca can see what she thinks are demonic butterflies since she can remember. They show up with all tragic events, but their wings seem to be some kind of burning portal. Her visions become more frequent after her mother's death. After another attack from her father, she finds out her mother left her best friend letters to give out at certain times to people. What secrets was she hiding? Why did she give the letters to Seiko? Why should Remedy, her brother, be dangerous?