The sisters' VAs have apparently been doing a radio show together, and I guess this is somehow related to that? The "angai" in the title is replaced with the word for "world fair". They seem to be up on Youtube if you want to hear them banter in Japanese.
https://www.youtube.com/watch?v=cMUjDKmwWEM
https://www.youtube.com/watch?v=NEV0vTlvrU0