Hello! That sounds like an exciting trip. Here are some detailed travel tips to help you with your journey to Sendai, Matsushima, and Tsuruoka in Japan.

Best Time to Visit:
The best time to visit these places is during the spring (March to May) when the cherry blossoms bloom, or in the autumn (September to November) when the foliage turns vibrant hues of red and yellow. Winter can also be beautiful if you don't mind the cold, especially during the Snow Festival in Sendai in December.

Route and Accessibility:
Sendai is easily accessible by Shinkansen (bullet train) from Tokyo, taking about 90 minutes. Matsushima is a short local train ride from Sendai. For Tsuruoka, you would need to take a bullet train from Sendai to Niigata and then a highway bus. Remember to purchase a Japan Rail Pass for unlimited travel on JR trains which will be cost-effective.

Accommodation and Booking:
There are lots of accommodation options in all three places, ranging from budget guesthouses to luxury hotels. Some hotels in Matsushima offer views of the bay. Booking in advance through platforms such as Booking.com, Expedia, or Agoda is advisable.

Clothing and Essentials:
Pack according to the season - warm clothes and boots for winter, and light clothing with a sweater or windcheater for chilly evenings in spring or autumn. An umbrella, sturdy shoes, and sunscreen are recommended. Don't forget your camera!

Health and Safety:
Japan is generally safe, but always ensure to follow local traffic rules, keep an eye on your belongings, and stay aware of your surroundings. Medicine should be packed with a prescription if necessary and check if your health insurance covers travel.

Local Etiquette and Respect:
When visiting temples or other religious sites, show respect by following local customs. Avoid pointing and shouting in public places. Tipping is not customary in Japan, so do not feel obligated.