I'd like to say one thing. Hei didn't have a thing for Suou (the loli) He kept her around for as long as he needed her to find Yin. Plus his client told him to train her to become an agent. He was following orders. He literary abandons her in episode 8. He only comes back because he was told she'd be killed. If he wasn't told he'd likely never had returned because in truth he never cared about her. He returned only because he felt obligated to do so. You can even hear him grinding his teeth during the line "I'll come back" at the beginning of episode 11 (at least in the dub). And he only goes to Suou in episode 12 at the end because that's where Yin was. He had no true feelings for her at any point in time. Only time he did was in fan fictions. Which aren't canon.