Preferably end of October or early November! AUTUMN <3 or SPRING NAMAN Here's the approximate schedule per region https://www.kyuhoshi.com/japan-autumn-foliage-forecast/

• Tokyo ulit + Enoshima/Kamakura + Nikko (may colours na ng October) + Kawaguchiko / Fuji Five Lakes (mid-November)
• Fukuoka + Hiroshima pero ang mahal ng train
• Takayama and Shirakawago via Nagoya
• Sapporo
• Osaka + Kyoto + Nara (stay longer in Nara?) + Kobe + Himeji Castle