"They corrupt because they linger. the chain that once connected them to their bodies breaks at death, and that chain degrades as they stay in the living world. It's a very painful process, becoming a hollow." One that Ichigo was all too familiar with based on how he'd reached his shikai.

"Oh yeah, but he won't hurt anyone. Whatever magic this train has makes it so he can eat normal food, so he's too fascinated tasting things for the first time that he can remember."