You treat everyone nicely, even if they don't deserve it. Now, after Lilia pointed it out, he realized that he had developed feelings for you. His pride would never let him tell you, but he wants to show you. So, he doesn't call you human anymore. He'll buy you little gifts or walk you back to your dorm after school. He always makes some kind of excuse, so you won't suspect anything about his new behavior, but it's quite obvious that he does, in fact, have feelings for you.