In March, 2018, new rail pass, “Greater Tokyo Pass” was launched in overseas tourist market. This new deal covers all subway lines in Tokyo and major non JR railway services in Tokyo and surrounding area. Both Haneda and Narita airports are covered by this pass. You can start using this pass right after you arrive in Japan.
Yokohama and Kamakura are very popular places to visit from Tokyo as day trip. Of course you can visit these places from other places, like Osaka and Kyoto. But there are several routes to get Yokohama and Kamakura from Tokyo. If you visit these places from Osaka, Kyoto and Nagoya, you will consider to drop by these places on the way to Tokyo. But is this a right way. Should we go to Tokyo first and then go back to Yokohama?