Getting to the Ferry Terminal   

By Train
Take the Senseki Line from Sendai Station to Tagajo Station.  From there, a taxi to the ferry terminal takes about 10 minutes.

By Bus
Miyagi Kotsu buses depart from Stop # 34, in front of Sakurano Department Store (West of Sendai Station). The bus takes approximately 39 minutes; one way fares are Y490 for adults and Y240 for children.  
For bus times see http://www.taiheiyo-ferry.co.jp/noriba/sendai.html (Japanese only: 仙台駅発 = departing from Sendai Stationフェリーターミナル着 = arriving at the ferry terminal; フェリーターミナル発 = departing from the ferry terminal 仙台駅着 = arriving at Sendai Station).