Chōshi (銚子) is a city in Chiba Prefecture.
Limited express Shiosai (しおさい) trains from Tōkyō on the Sōbu Main Line cost ¥3,510 for an unreserved seat or ¥3,820 for a reserved seat, and take about 1h40 for the whole trip. Be forewarned that currently the last Shiosai leaving Chōshi at 18:40 does not stop at Tōkyō Station but terminates in Shinjuku at 20:42. Missing this will require taking several local trains, most likely transferring at Chiba. The entire trip by local train costs just ¥2,210, but takes about two and a half hours.
All services mentioned above are fully covered by the Japan Rail Pass and the JR East Pass.