One of the most popular spots to see red leaves in Japan is the Maples Corridor or "Momiji Kairou" at Lake Kawaguchi. Momiji means red leaves and a "Momiji Matsuri" festival is held every year from the end of October to mid November with road stalls and romantic night illumination from sunset until 10pm, so it is a popular destination during November for people to see both Mount Fuji and red leaves.
Best Time to View the Maples
The best time is usually from beginning to mid-November. If you want to catch Mt Fuji, the best time is actually early morning like 6-7am before the clouds roll in. Therefore the best way is to stay overnight at a lodging there and waking up early to catch both the red leaves and a fantastic Mt Fuji view. Skies become dark by 5pm so you can catch the red leaves night illumination for a while before you return.
Other Tips for Maple Viewing
It can get chilly at night so be sure to bring enough warm clothing. I definitely recommend staying at Lake Kawaguchi for 2-3 days (including going to Gotemba Premium Outlets or Fuji-Q Highland amusement park) to explore to its fullest and enjoy the beautiful scenery.