"Kujuku" means ninety nine in Japanese.
"ri" is a unit of length in old Japanese system of weights and measures.
It's the nearest beach from Tokyo.
Minamoto no Yoritomo (Japanese warrior and established a new government, the Kamakura Bakufu) ordered the measurement of the beach, and "99" arrows were stuck on the sand.
It's said people started living in this area about 500 years ago.