We went to the Tanabata festival in Shimizu last week
Its a pretty good place to see Tanabata decorations and stuff.
Sendai is bigger, but boring, Hiratsuka is more crowded, so this is the best place to see the decorations.
There's some really good stuff here and its near the sea and the stations, has lots of food and drink stalls and things to do too!
Here's a bit about the significance of Tanabata in Japan...
[https://www.tripsavvy.com/japanese-tanabata-festival-1550123]
Here's some pictures...
Location information
● Japan, 〒424-0816 静岡県静岡市清水区真砂町5−25
Related link
● http://shimizutanabata.com/