Also known as: Misaki Castle (三崎城); Koajiro Castle (小網代城)

Arai Castle, a natural fortress located on a cliff at the tip of the Miura Peninsula, is surrounded by Sagami Bay on three sides. It was the main castle of the Sagami Miura Clan and where the last heads of the Miura Clan, Miura Yoshiatsu and his son Miura Yoshioki, fell to Houjou Souun in 1516 after a three-year siege.