A short walk from Takao-Sanguchi station leads to a lower tram station that you could take all the way up to Mt. Takao and the trailheads appear. The trail starts out steep with built in steps.
Up to Mt. Takao, the trail switches between steep and flat sections. I was at the summit of Mt. Takao, took only 80 min.
I left to continue to Mt. Jimba. That was a nice area with fewer people and more solitude. I really enjoyed the lush green. The route seemed relatively flat, but had a lot of ups and downs of a few hundred feet at best. And the parts that actually go up are steep.
I got at the top o f Mt.Jimba about four hours after I've left Mt. Takao. Unfortunately the clouds ruined the potentially nice views in all directions from Mt.Jimba, but at least it had this, whatever it is.
I would highly suggest this hike to anyone who has a day to hike while in Tokyo. It’s not the best of Japan, but quite feasible and really nice.