In Gantz issue 282 he meets Kurono, and tells him that the girl he used to have a crush on, Natsu, is now his girlfriend, and brags about he used to bully Kurono all the time. Images are shown of their past, he beating him senseless.
In issue 325 Kurono meets Ryou and Natsu again, locked in an alien zoo, and initially ignores their pleas to free them due to Ryou bullying him in the past. He thinks better of it, and then shoots the transparent barrier before them, shattering it.