Arrived at Sendai by a train, and tried my luck again with couchsurfing and fortunately this time I had a very nice and friendly Japanese girl accept me as a host, and she had great English so we could really talk about a lot of stuff and even tried to teach each other our native languages!
After a night at her house and trying to see what I can do with my limited time, I decided to go to Onuma Quasi-National Park.
My decision was a good one, that was a beautiful place that offered a boat ride as well as some min-islands to explore. I recommend going there if you're in Sendai! There isn't much to explain here, once you go there you'll pretty much know what to do and where to go. Arriving there is by a train from Sendai.
After all this, I took another Shinkansen to Tokyo which was my last stop before going back home.
Fascinating and helpful reading about these towns and destinations in Japan, places I would not have known about reading where to go.