Seraph of the End x Yandere/Yangire Simulator

People may have heard of vampires and yanderes. But what happens if you mix two different worlds together and in a different way? A Seraph of the End x Yandere Simulator crossover story. The world came down with the virus, and 10% of humans survived. Ayano Aishi, or Yandere-chan, survived with her little brother (y/n) and found her sempai Taro Yamada at Sanguinem. She killed some people and got her sempai to accept her feeling. However, one human found out about what she did. They got their group of friends and killed Ayano and Taro. A few vampires, including Ferid, let it happen because they thought it was entertaining. (y/n) saw as his sister was killed. He snapped and became more like a Yangire who kills out of hate and revenge. He vowed revenge on all of them one day. A few years later, (y/n) was ready to start killing from his family's methods. He also had a tape recorder to record his logs of each week of hunting and killing his targets. Will he succeed in avenging his sister? Is there something else going on that (y/n) doesn't even know? sadistic