What's this celebration in Japan?

We saw a couple of groups in the streets of Tokyo, Japan last sunday (May 28, 2017) engaged in some kind of celebration but couldn't find anyone english speaking around to explain to us what's going on.
Does anyone happen to recognise what celebration this may be?
One of the groups near Shinjuku train station...
Wall painting in Oshiage metro station depicting the same thing:
Best Answer
Perhaps the biggest festival in Tokyo at the end of May is the Sanja Festival. If you were in Asakusa, then that is probably the right answer.
Apparently, as you were in Shinjuku, the Hanozono festival is also possible.
Pictures about "What's this celebration in Japan?"



Rnbstylerz \u0026 AREES - WHAT
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Karolina Grabowska, Karolina Grabowska, Rakicevic Nenad, cottonbro