千本桜 (Senbonzakura)

Background
This song was originally uploaded onto Nico Nico Douga on October 17, 2011. It quickly became one of Miku's most popular songs with over 4,000,000 views to date.

This song seems to be about westernization in Japan, which happened mainly after WWII. Despite having an upbeat track, the song is actually kind of depressing, with some of the lyrics saying things like "Not even a lamenting song is available." and "This is a banquet inside a steel jail cell."