According to the notebook left on his desk, Yuu was doing some research for Kei Amakura.
His notes are full of accounts of old urban legends, and newspaper clippings about disappearances and people who were "spirited away".
RN:Yuu's research
Rei's notebook: Yuu's research
Replaced by: Disappearances
Obtained: Going to Yuu's Room and reading the research notebook on his desk.
Type: Incidents
TBA