Shuttle bus time table is here.The bus departs from Sendai station in front of West Exit with number 13. Note that there is no sign of the bus stop. But if you wait around the exit you'll see a bus with "green green" on its side just before departure time.
The West Exit 13 is on the first floor (Sorry, it's American style of counting floors ;-) ). After you pass through a ticket gate of Shinkansen, please go down stairs and you reach the second floor. On the right, you'll find escalators. (if you pass through South Exit of Shinkansen, you'll find them after 10 meters' walk to the right.) Please go down to the first floor there, then you'll be at the West Exit 13. If you go out a wrong exit, you should find the taxi terminal. The shuttle bus stops on the right of it.
Time tables are here. To transfer to Senzan Line at Sendai station, please go down stairs leading Central Exit when you get off a Shinkansen. Then follow the sign saying "Local line entrance". Please turn left after you pass through a ticket gate of Shinkansen. Senzan Line departs from the platforms 6 and 7.
The last bus leaves Sakunami station at 19:32. If you miss the last bus leaving Sakunami station, please call the hotel (phone: 022-217-5450). You can ask the hotel to pick you up at Sakunami station.