Green & Clean water with horse riding event would be held on the 8th Oct 2016 in Tokyo Hino city.
There are 3 courses (walking only, walking with lunch, and walking, lunch, and horse riding experience) for this event and you would be a great experience the nature of waterway, watermill, ricepaddy, etc even in Tokyo!
Details on Facebook page ; https://www.facebook.com/events/1589039028068250/