Chizu Sakanaka
The owner of the inn that Natsumi Takashi goes to in episode 8. It is told that while she was young, she came to like a person, known as Keiichi, who was around Takashi's age. However, Keiichi was sick. One day when he fell seriously ill, Chizu went to Sasafune to get mermaid blood. She fed Keiichi the blood and he was later on transferred to a faraway hospital. Thinking that she had made Keiichi's life miserable, she spends everyday waiting for him at a train station. Spoiler It is revealed at the end of the episode that Sasafune did not give a vial of mermaid blood to Chizu. It was a vial of grape juice.