Actually, this is a good chapter to show how the MC isn't completely heartless. Sure he's self-interested, but there's more to this than what it seems. Buying slaves seems hypocritical, granted given his circumstances, but he immediately changes his mind when he says he's going to find a slave that's easy to control when he finds one that has more fight in her than he expected. He clearly empathizes and sympathizes greatly with her story because he's been through the same traumatic experiences, and knows the drive of revenge. He doesn't want to treat her unjustly and is willing to punish the slave dealers if he wants her to do so. Additionally, when she brings up the "level cap break," he gives a saddened expression, because he knows that in order to do so he'll have to give her his semen, something he is every clearly uncomfortable with, but is willing to do if it means she can get her vengeance. It's an interesting demonstrating of MC's more human characteristics.