Well that was unexpected. William was simply doing his duties as a reaper, collecting people's life reels, when suddenly a dead woman arose as a reaper. Oh for the love of-

The higher-ups apparently want her to be his apprentice. He has to train her now and teach her everything about being a reaper if he doesn't want to be executed. He was originally annoyed but they picked a good personality match for him. He found himself bonding with you and stalling his teaching to keep you close to him.