These are memorial towers for Anjin Miura, the British foreign adviser to Ieyasu Tokugawa (the first shogun), and Anjin's wife, who was Japanese.
Anjinzuka is a set of memorial towers built by the will left by William Adams, a British man with the Japanese name Anjin Miura, who played an active role as a foreign adviser to the first shogun of the Edo Period (1603 to 1868). It is believed that the tower on the right is for Anjin, and the one on the left is for his Japanese wife. Anjinzuka is registered as Japan's historic site. The name Anjin means a coastal pilot, and it is said that Adams's was named Anjin because he was a navigator. He had earned Ieyasu Tokugawa's trust to be given a territorial land in Hemi-mura in Miura-gun (the current Yokosuka area) and worked as a foreign adviser. He had also introduced the Western civilization to Japan such as gunnery, marine architecture, and navigation techniques. The Tsukayama Park, where the towers are, is known as a famous spot for sakura cherry blossoms. During the sakura season every year, the William Adams Cherry Blossom Party is held in commemoration of Anjin Miura. It is a 25-minute walk from either the Anjinzuka Station or the Hemi Station on the Keihin Line.