The general framework
Japan's Civil Aeronautics Act restricts drone flight in a range of situations — near airports, above a set altitude, over densely populated areas, at night, or beyond the operator's direct line of sight — with permission required from Japan's Civil Aviation Bureau for most of these. Given Osaka's dense central districts and its proximity to Kansai Airport, a large share of the most photogenic spots in the city fall under some form of restriction by default.
Local, site-specific rules
On top of the national rules, individual parks, temples and shrines commonly prohibit drone flight outright on their own grounds, including popular spots like Osaka Castle Park — a blanket local rule that applies regardless of whether the national airspace restrictions would otherwise allow it.
What to actually do
If flying a drone matters to your trip, check Japan's current civil aviation drone regulations and any specific site's own rules well before you travel — permits, where required, generally need to be arranged in advance rather than on the day. For most visitors, it's simpler to treat central Osaka as a no-fly trip and get elevated shots from spots like the Umeda Sky Building or Tsutenkaku Tower instead.