Lake Koyama ( 6.9 square kilometres ( 2.7 sq mi ) ) was once an inlet of the Sea of Japan .
Lake Koyama ( 6.9 square kilometres ( 2.7 sq mi ) ) is a brackish lagoon to the west of the mouth of the Sendai River .
Lake Koyama ( 6.9 square kilometres ( 2.7 sq mi ) ) , a brackish lagoon to the west of the mouth of the Sendai River , was once an inlet of the Sea of Japan .