Sendai is located approximately 350km (220miles) North of Tokyo on the Pacific coast of Honshu (The largest of Japan's four major islands).Sendai lies in the center of the Tohoku (Northeast) Region, one of the seven major regions in Japan.
It takes about 1 hour and 40 minutes to reach Sendai from Tokyo on the Tohoku Bullet Train (Tohoku Shinkansen). Sendai also has regular Flights to and from major domestic and International cities.

Further Information:
http://www.city.sendai.jp/kikaku/kokusai/english/index.html

How to access to Sendai by Japan Railways

If you arrive at Narita International Airport, I would like to recommend Japan Railway.
Because it operates in exact time schedule and has many traffic.

Narita has two International Terminals,
Terminal 1 mainly uses
North Wing: Air France, KLM, Northwest, American Airline, British Airways, Cathy Pacific, Virgin Atlantic.
South Wing: Star Alliance Group, United Airlines, Singapore, ANA, Scandinavia, Lufthansa Thai International,

On the other hand Terminal 2 uses Japan Airline, Qantas, China Airlines, Finn air and so on.

Please, purchase the ticket from Narita to Sendai with reservation at Reservation Desk in advance. ((Midori no Mado-guchi)
If you would like to travel around Japan, I recommend purchasing the Japan Rail Pass.

Further Information:
http://www.jreast.co.jp/e/index.html
http://www.senat.co.jp/timetable/

From Narita to Tokyo

Narita Express (N'EX) operates between Narita International Airport and Tokyo Station.

Narita Express (NfEX) is

Less than 1 hour
N'EX takes just 53 minutes to cover the distance between Tokyo Station and Narita Airport.

No more traffic jam
Car and bus travel to the airport is time-consuming and unreliable.
On N'EX you do not have to worry about crowded highways and limited parking space anymore.

Frequency
N'EX usually runs every one hour, and every 30 minutes at peak hours.

Tokyo Station

If you take the train, you may feel hard to transit at the Tokyo Station.
Please, check the instruction in advance.
You get off the Narita Express at the B5 platform, go up to the B1 level, then look for the Tohoku Shinkansen Entrance (Green sign). It will take about 20min by walk to transit the station.

If you come to Sendai by Tohoku Shinkansen, Please choose the Hayate Express.
Hayate Express is the fastest (only 100min) and the most luxurious train.

Ticket Fare:
From Narita International to Sendai JPY 6,830
Reservation:
From Narita International to Tokyo JPY 1,660 (Normal) JPY 3,660 (Luxury)
From Tokyo to Sendai JPY 4,810 (Normal) JPY 8,810 (Luxury)

How to access to Sendai by Air

Between Narita Airport 1 and Sendai airport, ANA operates 2 flights for a day. It is mainly
Connection with ANA or Star Alliance Groupfs International flight and its capacity has only
50 passengers on board.
If you would like to reserve the Domestic flight from Narita to Sendai, Please choose the
Star Alliance Group first.
Generally domestic airlinefs reservation starts 2months prior to departure. If you need any assistance, please contact me.

The schedule is follows

Fare: JPY 13,700 (discounted) JPY 18,600 (Normal)

From Narita Airport 1 to Sendai

ANA-3131 Narita Airport 1 (10:30) Sendai (11:35)
ANA-3235 Narita Airport 1 (16:55) Sendai (18:10)

From Sendai to Narita Airport 1

ANA-3232 Sendai (08:15) Narita Airport 1 (09:25)
ANA-3234 Sendai (16:05) Narita Airport 1 (17:00)

Sendai has regular lights to and from major domestic cities.
If you board from long distance flight, we recommend the Nagoya Chubu Airport (NGO).
Nagoya Chubu Airport has easy access from international to domestic flight on the same Terminal building, besides between Nagoya Chubu and Sendai we have 5 flights daily.
http://www.centrair.jp/index.html

If you fly to Sendai from Kansai International Airport, you Have to move to the Osaka Itami Domestic Airport. You will take more long time to transit than Nagoya Chubu Airport.
http://www.kansai-airport.or.jp/