Hello! That sounds like an exciting trip! Here are some tips to make the most out of your travel to Tokyo, Nikko, Sendai, and Aomori.

Best Time to Visit:
The best time to visit these cities in Japan is during the spring (late March to early May) when the cherry blossoms are in bloom and the weather is mild, or during the autumn (late September to early November), when the stunning fall foliage is on display.

Route and Accessibility:
All these cities are accessible by Japan's swift and efficient train system. From Tokyo, you can travel to Nikko, Sendai, and Aomori using the JR East Rail network. The Japan Rail (JR) pass can be very cost-effective if you plan to travel a lot.

Accommodation and Booking:
Accommodations range from luxurious hotels to traditional Japanese inns (Ryokan) and budget guesthouses. It's best to book in advance, especially during peak season and on weekends. Also, check out Japanese-style Airbnbs for a unique local experience.

Clothing and Essentials:
Based on the season, carry appropriate clothing. In cooler months, pack warm clothes and a good pair of shoes. During the rainy season, umbrellas are useful. Regardless of the season, carry a travel adapter, toiletries, medicines, and avoid carrying too much cash as Japan is largely cashless.

Health and Safety:
Japan is overall a very safe country with excellent healthcare facilities. However, do ensure you've taken travel insurance for emergencies. Also, keep yourself hydrated and try to avoid the rush hour in major cities.

Local Etiquette and Respect:
Japanese people appreciate it when visitors respect their customs. When visiting shrines or temples, follow proper etiquette, such as washing hands and your mouth at the purification fountain. Bowing is a common gesture for greetings. And remember to always take off your shoes before entering a home or a traditional inn.