Based on my current knowledge, traveling to Japan is generally safe, but safety conditions can change over time. It is recommended to pay attention to the local security situation and possible risks in Japan before planning a trip.

Regarding the number of days to travel, it depends on personal interests and schedule. Generally speaking, 7 to 14 days can provide a more comprehensive experience of Japanese culture and scenery. However, the specific number of days needs to be determined based on personal travel plans and budget. When planning your itinerary, consider the following suggestions:

  1. Tokyo: 3-5 days, you can visit Asakusa, Akihabara, the Imperial Palace, Tokyo Tower and other attractions.
  2. Kyoto: 2-3 days, you can visit Kinkakuji Temple, Kiyomizu Temple, Fushimi Inari Taisha Shrine, etc.
  3. Osaka: 2-3 days, you can visit Shinsaibashi, Dotonbori, Osaka Castle, etc.
  4. Hokkaido: 3-5 days, you can visit Sapporo, Furano, Noboribetsu, etc.
  5. Kyushu: 3-5 days, you can visit Fukuoka, Nagasaki, Kumamoto, etc.

Please adjust your itinerary according to your personal interests and actual conditions. Before traveling, be sure to pay attention to the weather, traffic and accommodation conditions at the destination to ensure a smooth trip.