http://www.sendaiareapass.jp/en/index.htmlAlso similar "Sendai Marugoto Pass" for 2 days you can buy.
http://www.jal.co.jp/domtour/jaldp/sdj_skyjourney/img/16shimo/pic_free...(not only for foreign travelers)
How to get in Sendai?
If no car rent or taxi plan and started JR Sendai stn,
1) JR train until Ayashi stn, then Sendai city bus until Fall.
2) JR train until Nagamachi stn, then Miyagi kotsu bus until Fall.
3) Sendai city Subway until Nagamachi-minami stn, then Miyagi kotsu bus until Fall.(same 2)'s bus)
4) Miyagi kotsu direct bus until Fall via Nagamachi(as 2) and Nagamachi-minami stn(as 3).
(Nagamachi-minami stn placed btw Nagamachi and south last stop Tomizawa stn)
But all buses are not so many, be careful.
4) fare is 1100Y/oneway adult, about 70 min travel, longest.
All trains and buses are regular, no booking.
Also you can take Rapid(some stns skip type) train, not only Local(all stns stop type).
For Nagamachi some Rapid won't be stopping.
City Subway is only all stop type, no rapid.
Akiu fall : Akiu Otaki(秋保大滝 in Japanese)
If would like to see at near under the fall,
across the downstream bridge then enter forest road down
about 10 min walk fr viewing platform near bus stop(バス停 : bus-tei).
https://youtu.be/fdtQkv7nkmo(Please don't go down after heavy rain.)
A lot of amount of water season is in April and May by snow melting of mountains,
and mid June and early July in the rainy season.