The Koito River originates from a deep valley in forests around Mount Kiyosumi in the Bōsō Hill Range.

[4] The Kimitsu Works sits on the north bank of the Koito River where it empties in Tokyo Bay.

[5] The Mishima Dam was built on the Koito due to prevent drought on the upper and middle parts of the river, and the Toyofusa Dam was built on the upper part of the river to prevent water shortages and supply water for industrial purposes.

[8] The earliest settlements in the southern part of Chiba Prefecture were via the numerous small rivers on the Bōsō Peninsula.

The area around the mouth of the Koito River is the historical center of Chiba Prefecture's nori seaweed industry.