Hmm... Otoha has no problem with Zelman, really. He finds him kind of amusing. He reminds him a lot of people he met in the Yakuza, except he actually does have the balls to back up any threats he might make.
He doesn't have a problem with the blood thing, despite how it sounds. He'd freely give Zelman blood if he needed it. He does kind of want to get to know Zelman more but he doesn't know how to go about it.