Rex explained everything: being paired by Lord Death, their first mission, meeting the warlock and the Kishin, and ending with coming to Stein's place. "Stein believes it's some kind of rebound," finished Rex. "When I used Wolf's Death energy, there was a void, and my Holy energy took its place. I don't wanna hurt her again. I've already lost one partner..." His mind had flashbacks to the Paris Incident: eating croissants at a cafe, waiting in Notre Dame for the Kishin, killing it, and Sora...
Rex shoved the memories back into their dark cage. "I'm putting in a request to your father, to make sure that this never happens again."