Hinata Urashima, also known as Grandma Hina, was the original manager of Hinata House. After retiring to travel the world, she entrusted Keitaro with overseeing the Hinata Inn.
In the manga, Grandma Hina was aware all along that Naru was the girl Keitaro had promised to attend Tokyo University with. She also knew the location of the Liddo-Kun shaped time capsule that Keitaro, Naru, and Mutsumi buried beneath the sandbox when they were children.
Although she only appears briefly in both the manga and anime, her visits and actions significantly impact everyone, especially Naru and Keitaro.
(Source: Wikipedia)
