I really like that one of the biggest similarities between Iason and Riki is that they are both very rebellious people. I think a lot of us (even me i'm not shaming anyone) forget how similar they are in this regard. Iason may indeed have developed this after meeting Riki, and he may not show this part of his personality as much as Riki does, but it is still something that forms part of how Iason is as a person.
Someone may say Iason's actions in the novel don't exactly make him someone rebellious, but it's more than his actions; that hidden aspect of Iason can be seen in his fixation on Riki's rebellious personality. Iason doesn't find Riki's personality fascinating just because of sadism or curiosity; Iason is fascinated by it because Riki represents all he wants to be. Iason wants to be human; he wants to be rebellious, but he can't: he's half-man, half-machine, close enough to humanity to yearn for it and far enough to never reach it. The only way Iason can experience any of this, rebellion and humanity, is by loving Riki.
