I happened to peek this Japan forum and found your post. Welcome back to flying!
Finding flight area, especially for large or nitro plane is a challenge. Many fliers go to park early morning to fly electric. I live in Chiba, near Disneyland. There used to be open area where we can fly nitro but no more. I am driving 50km to the field every weekend. Like Yokosuka, it is very windy here close to Tokyo bay. You will soon get used to fly in the wind.
You are lucky you are close to 1 of the best 2 seaside slope gliding areas in Tokyo. You can drive down to Jyoga-shima and see there. Slope flying may not be so popular but once you find the fun, you are all set.
They have web site. They like to fly high wind. Flying season is just starting. I am sure you can find flyers there on south wind days.
Location should be around south ridge of Jyogashima park