Given the things Muraki is capable of, I figured this would be a good idea. Fill it out for your characters and I'll use it as a reference for scheming. Nothing will actually happen without me talking to you first, but this is still a place to start!
Can Muraki:
Interact with your character?
Manipulate your character?
Toy with your character's mind/memories?
Injure your character?
Kill your character?
Flirt with your character?
Sexually harass your character?
Rape/molest/sexually assault your character?
Frame your character for murder?
Drain your character's life energy if they're injured or dying?
Exploit whatever mental weaknesses your character has?
Other notes/questions?