Is Matsushima a restricted area?

s Matsushima a restricted area after the tsunami

No, Matsushima suffered only minor damage from the tsunami compared to other places along the coast. Most of the damage has been repaired in the meantime, and most tourist attractions were reopened over a year ago.

Here is a trip report from April 2011:
http://www.japan-guide.com/blog/schauwecker/110421.html

And photos in autumn 2011:
http://www.japan-guide.com/blog/recovery/111018.html

Even in the more heavily damaged coastal areas there are no restricted areas. The only restricted area are a few kilometers around the Fukushima Daiichi nuclear plant.

Here are some basics:
http://www.japan-guide.com/news/0018.html

No, not at all. In April we went by JR to Hon Shiogama and then by boat from there to Matsushima, where we spent a wonderful day.
There is still evidence of the damage caused by the earthquake and tsunami, but the day trip from Sendai was well worth it.
Enjoy!

The restricted area is only around the defunct Fukushima Daiichi reactors. Tsunami affected areas apart from that are not restricted areas (Matsushima was not destroyed although some damage has been done).

It's a nice place to visit.