I've read Giovanni's app and it seems like the two of them have contrasting histories (Giovanni being raised as the 'weakest' of a group of children while Julius was considered the best subject of his group and raised in total isolation) so they have vastly different attitudes despite essentially being modified to play similar roles (fighter/executioner). Seeing that Giovanni is good at his job. I figured that if they go on a mission together Julius would give him recognition for the part he plays + be mildly interested in interacting with other people who have similar histories, since they're both friendless people, and we can start off an acquaintanceship from there?

Let me know if you've got any other ideas, this was the one that just came to me!