Actually, Lulu died and Hotaru's mom didn't want to upset Hotaru, so she didn't tell her. But Hotaru desperately was searching her cat and got in car accident at 5 in the morning near the old house. During coma after the accident, Hotaru saw Mizuki's soul. Also, she saw Lulu's soul who was calling her to go away from strange fence. Even after the accident, when Hotaru came back from hospital, she kept searching for Lulu. Because of it, she met Mizuki again, who was wandering in the old house as ghost. Eventually, her mom told her what's actually happened and show her the grave. Lulu's soul became companion of Adam Lang's soul.
In the old haunted house, Hotaru found another cat, who looked just like Lulu. Hotaru called him Adam. He kept company Eve, while kids were trying to solve the mystery. Eventually, Hotaru took that cat in, instead of deceased Lulu.