A female flying down the Katsura River (Kyoto city), October 2011.
Black Kite is a really common and widespread bird in the region, there can be gatherings of as many as 50-100 birds over the Kamogawa (Kyoto city) outside the breeding season. Even bigger numbers ring Lake Biwa and any fishing port will be full of them.
In early May Black Kites can look very worn and unkite-like.
Seven species of harrier have been recorded in Japan which sounds great but only two, Hen and Eastern Marsh can be considered in anyway common or likely to be seen by visitors. Of the others Pied is rare, a male on Hegurajima is the only one I've seen, and the others extremely so.
Eastern Marsh Harrier is a winter visitor to Kansai and is reasonably common over reedbeds, or open arable country within reach of a reedbed for roosting. They can be seen quartering the riverside reeds along the Yodogawa from the centre of Osaka right up to Kyoto. Birds are fairly common in the Lake Biwa area, along the lake side or neighbouring fields. Lake Sainoko, near Omihachiman, half way down the east side of Lake Biwa, is an important roost site. The road along the north side of this lake is a good place to get close fly-by views in late afternoon.
Eastern Marsh Harriers at Lake Sainoko, Shiga.
Hen Harriers are less common than Eastern Marsh but can be found in most of the same places, though they aren't likely to be found in Osaka and numbers further up the Yodo River seem to have dropped in recent years. Lake Sainoko is probably the most reliable place to find them. Males are far less common here.
Hen Harrier at Lake Sainoko, Shiga.