I can kind of understand that villain system. If we put it in a stupider series, like DXD, or a normal series, like Ranma, then it's like you fucked Issei's mom or Ranma's mom, and then took a bit of their luck, had kids with their moms, took more luck, so now Issei can't beat his enemies as easily, or the girls won't love him "just because he's kind", or even get that stupid red hand glove