Hi,
https://www.openstreetmap.org/way/1282847262 is not a riding centre, it is a riding arena (see http://kashiwa-rc.jp/, http://kashiwa-rc.jp/images/head_img05.jpg). In OSM riding arenas are usually tagged leisure=pitch + sport=equestrian. In JOSM you can use the preset for sport=equestrian to do that. The tag leisure=horse_riding should be used for the whole riding centre (in this case it can probably be added to https://www.openstreetmap.org/way/472634113). Compare https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dhorse_riding and https://www.openstreetmap.org/way/1216574681 (example).