You will need a three different visas - Nepal, India & Bhutan.
Nepal: All foreigners, except Indians, must have a valid visa to enter Nepal. Nepali embassies and consulates overseas issue visas without any problem. One can also obtain on the spot when you arrive in Nepal, either at Kathmandu’s Tribhuvan Airport.
Bhutan: All visitors traveling to Bhutan are required to obtain the visa prior to arrival in the country. One cannot obtain the visa at their respective countries. We will organize the entire visa procedure for our guests. Once the trip is confirmed, we will send the Visa application form via email, the clients do not have to send us their passport. The final visa stamp will be issued upon arrival in the country.
Sikkim: You will need an Indian visa which can be easily obtain through one of the embassies/consulates located in your country. Apart from Indian visa. visitors also require a Inner Line Permit for entering Sikkim which we will organize for our guests.