Which Railpass to buy in Japan?

visiting Japan in April 2018 for 10 days travelling from Tokyo to Heroshima and back through about 6 cities in between.We will like to buy a 7day rail pass that also includes bullet trains.Confused about which Railservice(From many) pass to buy?
Seems very confusing as there seems to be many Rail companies. Which rail pass will be right for the area we are visting?We would prefer first class pass.

The only pass that will get you from Tokyo to Hiroshima and points in between is the full JR Pass that is valid on all JR lines in the country from all JR companies. It covers all the bullet train lines. They have a first class "Green car" option, but the regular bullet trains are quite nice already.

This one: https://www.japan-guide.com/e/e2361.html
(Check out the small list of exceptions on the specific bullet trains you can take with the pass)

If your trip is 10 days, you will need to be mindful of when you activate the 7 day pass so it doesn't expire before you need to make the return trip.

In 10 days you'll be rushing through 6 cities between Tokyo and Hiroshima....how much time will you actually spend on sightseeing and savouring things vs travel time and crossing things off your list?

For sure the 7-day JR PASS will work for you covering travel between those places, but like stated above you need to be careful when you activate it so it can be valid to take you back from Hiroshima to Tokyo (beware though it could be in excess of 5 hours depending on your connections).

The pass needs to be purchased from outside Japan, so check where you can order it from in your country. You will mostly be given a voucher that can exchange for the actual pass when you're in Japan. Within Tokyo and cities like Osaka and Kyoto using a Suica card or similar should suffice, and use the JR pass for travel between cities. Consult the hyperdia website to plan your route of travel and figure out the travel time between the cities you plan to visit. Also, If you are going to Hiroshima, there is a hop on and off bus which is covered by the JR pass.

The 14 day pass is cheaper than the Tokyo-Hiroshima return trip.