Running routes recommendations (Tokyo, Kyoto)

I'm a beginner runner, currently training for marathon. I'll be visiting Japan some time later this year, and I'd like to plan some runs to fit my training schedule. I have some experience with regard to navigating the country (Tokyo surroundings, primarily though :), and I have minimal experience running in/around Tokyo. Right now, I'm looking for some lesser known routes, that would offer some nice views, or unusual places. To give you an idea what I'm looking for: so far I've ran on Odaiba, around Imperial Palace and in both Shinjuku and Ueno parks. Right now I'm after two kind of things:

* ~10-15km routes, with up to ~400m of a climb.
* 28-30km routes, as flat as possible.

I have a couple of ideas laid out already. I can probably come up with more semi-sensible ideas for routes within Tokyo or Kyoto - running along a river seems like a reasonable plan B. I'm way more curious about routes like this one, where you have a bit of a climb, potentially a view, and some nice-looking feature (Arashiyama bamboo forest). From what I've gathered, there's plenty of valleys around Tokyo, that are within 1h train ride, and offer good hiking/running opportunities, but it's bit hard to decide what's worthwhile. :D

Thanks for any recommendations!

https://en.japantravel.com/guide/8-best-places-to-run-in-tokyo/30764

Note, Tamagawa has a very long uninterrupted running course (and cycling). On a clear day, Fuji is part of my scenery, otherwise the riverside and the hills on the edge of the Kanto Plain are fine for me.

If you are on the west of the city then the Tamagawa is the obvious answer for a longer run. After saying that I did a google search for "running Tokyo" and lots of people seem to agree :) I assume you have already discovered Namban Rengo? https://namban.org/ At the very least their "running resources" page has some useful info. Or if you prefer beer http://samuraisports.org/clubsgroups/mikkellerrunningclubtokyo/