Kōka (甲賀市) is a city in Shiga prefecture, Japan.
Kōka is well known for its ninja history (Kōga ninja clan), unique ceramics and position on the Tokaido Road. The Kōga ninja clan were rivals of the nearby Iga ninjas. Unlike the Iga ninja, whose power was well-known, the Kōga clan are said to have used stealth and deception to mask their size and power, creating fake rivals for themselves. In 1581, the two clans joined forces against Oda Nobunaga, but were defeated by Nobunaga's overwhelming forces, and the surviving members of the Kōga ninja went into retreat.
The ceramics produced in Kōka, known as Shigaraki-yaki, have been prized across Japan for centuries. Today you will see many small pottery shops lining the streets near Shigaraki Station.
The Tokaido Road was for centuries the main route from Kyoto to Edo (present day Tokyo). The road passes through the heart of Kōka, and two famous rest stations, Tsuchiyama and Minakuchi, are located here.
In 2004 the towns of Minakuchi, Shigaraki, Tsuchiyama, Kōga and Kōnan merged to form Kōka City.
Kōka has five stations on the JR Kusatsu Line. The largest station, Kibukawa, is about a 45 minute ride from Kyoto.
From JR Osaka or Kyoto Station, get on any regular, rapid or special rapid train headed for Kusatsu, Yasu, Maibara, Nagahama or Tsuruga. Get off the train at Kusatsu. From Kyoto this takes about 15-20 minutes. Do not exit Kusatsu station, and transfer to any train bound for Kibukawa or Tsuge (Keep in mind that trains bound for Tsuge will stop at all stations in Koka City, while trains bound for Kibukawa will only stop at Kibukawa). The train from Kusatsu to Kibukawa takes about 25 minutes.
Along with the JR train line, Koka has 4 stops on the Omi Railway and 5 stops on the Shigaraki Kogen Railway. Both of these railways can be accessed at JR Kibukawa Station. Koka also has an extensive bus network, with many buses departing from Kibukawa Station.
- Ninja Estate (Ryuhoji Konan-cho, Koka-shi; 9:00am-4:30pm, closed 12/27-1/1. Admission ¥600 adults, ¥300 children ages 6-12.) This estate was built over 300 years ago for the famous ninja leader Mochizuki Izumonokami. From the outside, this estate looks the same as the other homes in the area, however the inside clandestinely reveals the characteristics of a ninja residence. You will see a number of trap doors, false walls and hidden rooms that were designed to protect the home from potential intruders, . You will have an opportunity to see a display of actual ninja weaponry and other historical artifacts, You can even take a try at throwing ninja stars. The gift shop sells small souvenirs, and everyone can sample a specially blended health tea that the ninjas often prepared. Take the JR Kusatsu line to JR Konan Station. The Ninja Estate is a 20 minute walk from the station.
- Ninja Village (394 Oki Koka-cho, Koka-shi; 9:00am-5:00pm, closed Mondays and 12/27-1/1. Admission ¥1000 adults, ¥800 children ages 13-18, ¥700 ages 6-12, ¥500 ages 3-6.) Similar to the once hidden ninja villages that existed in the area, the Koka Ninja Village exhibits a number of transplanted ninja estates. With a plethora of contraptions and a throwing star training room, this is the place to go for a hands-on ninja experience. The attached museum offers an extensive 1,400 piece collection of ninja artifacts. Ninja uniforms are available for trying on and trying on and kids will enjoy the obstacle course of walls and ropes. Take the JR Kusatsu Line to Koka station. There is free bus pickup from the station to the Ninja Village.
- Shigaraki-yaki Ceramics Shigaraki is home to one of the oldest and most famous schools of pottery in all of Japan. As you exit Shigaraki Station and walk along the main road, you will see dozens of small shops selling ceramics that range from ornamental to practical. "Shigaraki-yaki," as the pottery is known, was first produced in the Kamakura period during the 12th century. Several centuries later, during the Muromachi period, Shigaraki-yaki gained prominence as an ideal ceramic for the traditional Japanese tea ceremony. Recently, some of the most recognizable pottery from Shigaraki are tanuki (a racoon-like animal) statues. Of course cups, plates, bowls and a number of other goods are also available.
- Minakuchi Castle  was built in 1634 as a way-station for Tokugawa Iemitsu in his travels between Tokyo and Kyoto. The current reconstruction dates from 1991. It's on the Omi Tetsudo Line, a five minute walk from Minakuchi Jonana station.
Many of the above sights offer a number of activities that go beyond simply "looking." Furthermore, Koka is an excellent destination for cherry blossoms (early to mid April), hiking and autumn foliage
Iga is the other ninja hot-spot in Japan, and isn't far away.