Here's beginning of an Asahi article about this video:
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Kumamoto Castle video goes viral with 400,000 views
February 01, 2016
By CHIE KOHARA/ STAFF WRITER
KUMAMOTO--A YouTube video to promote Kumamoto Castle starring popular dance duo Egu-Splosion has become an online hit, garnering more than 400,000 views since its release in late December.
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http://ajw.asahi.com/article/cool_japan/style/AJ201602010001
It would be nice if the video had English subtitle. As the article indicate, the song is filled with lots of interesting trivia about the castle.