Koka Ninja House

Koka ninjaMochizuki houseGenrokuhidden mechanismsKoka

Shiga · Koka

34.9183°N, 136.1674°E

This is the house of the Mochizuki family, head of the fifty-three Koka ninja households, built in the Genroku era and still standing on its original site — the only genuine ninja residence surviving in Japan rather than a reconstruction. From the outside it is an ordinary farmhouse. Inside it has a concealed mezzanine and third floor, a revolving door, a trapdoor, a rope ladder into the roof space and observation slits cut so that a room can be watched from above without being entered.

Koka and Iga, over the ridge in Mie, were the two centres of the practice, and Koka's specialisation was pharmacology — the household medicine trade that grew out of it kept several families in business into the modern era. The house is small, privately run, and shown at your own pace rather than as a performance.

Essential Information

Opening Hours

9:00 AM – 4:30 PM

Closed: Confirm before travelling

Entrance Fee

¥650 adults | ¥350 children | Group rates ¥600 and ¥300

Best Season

Year-round

Visit Duration

1 hour

Getting There

Access Information

Konan-cho Ryuhoshi 2331, Koka City. About 20 minutes on foot from Konan Station on the JR Kusatsu Line; about 10 minutes by car from Koka Interchange. Open 9:00 AM to 4:30 PM. Admission ¥650 adults, ¥350 children, with group rates of ¥600 and ¥300. The house has steep ladders and low openings and is not accessible for anyone with limited mobility.

Insider Guide

Premium

**It is the real thing, which is why it is small.** No shows, no costumed staff, no theme park. A Genroku-era farmhouse with the devices built into it, and you work them yourself. **Try the revolving door.** Visitors are expected to operate the mechanisms rather than look at them behind glass. That is the difference between this and the reconstructions. **Steep ladders and low openings.** The hidden floors are reached by ladder through gaps sized for someone crawling. Not suitable if that is a problem. **Koka's speciality was medicine.** The pharmacology that came out of the tradition turned into a household drug trade that survived into the twentieth century, and several Shiga pharmaceutical firms trace back to it. **Iga is over the ridge.** The other centre of the practice is in Mie, 40 minutes away, and treats the subject far more theatrically. Doing both shows the contrast. **Koka Real Ninja Museum is in the city.** A separate, newer facility near Koka Station with the historical exhibits, if the house leaves you wanting context.

View on Google Maps