さざなみ・
わかしお・
しおさい（E257系）

Operating along the Boso Peninsula are the Sazanami train on the Uchibo Line and the Wakashio on the Sotobo Line. The Boso Peninsula runs north-south, forming the eastern border of Tokyo Bay. The Uchibo Line (uchi meaning "inside") runs on the Tokyo Bay side toward Kimitsu, while the Sotobo Line (soto meaning "outside") operates on the Pacific Ocean side, generally carrying business and leisure travelers to Awa-Kamogawa Station. The Sazanami and the Wakashio are painted in blue, white and yellow, representing a Boso Peninsula motif for the blue sea, white sand and yellow aburana (rapeseed) flowers.

※しおさい号は別の形式で走行することがあります。