Hekikai no AiON

Tsugawa Tatsuya is struggling with grief after the death of his parents in an accident, burdened by a large inheritance he cannot use. Haunted by his father's final words, he questions his ability to live up to the family's expectations. He encounters Miyazaki Seine, a girl who appears to enjoy being bullied. Despite his friends' dismissive view of her, Tatsuya feels compelled to help, even after she tells him to stay out of her affairs. Seine hunts parasitic sea creatures that take control of humans and drive them to hatred. She has an immortal body and a creature named AiON that lures and consumes the parasites from within their hosts. Seine and the parasites instinctively attack each other. Despite this, Tatsuya remains determined to assist her.