Hana is a pivotal character in the Japanese tokusatsu series Kamen Rider Den-O. She is a mysterious young girl who has lost her memories, and her presence is intertwined with the time-traveling adventures of the protagonist, Ryotaro Nogami. Hana serves as a key ally to Ryotaro, guiding him through the complexities of time and the battle against the Imagin creatures. Her knowledge and insights are crucial in understanding the threats they face, and she plays a significant role in the development of the storyline and the dynamics among the characters.