To commemorate the release of their new album "EGG", flumpool have launched a special website for the album's lead track "Kaihouku". 

On "kaihouku.jp", you can view a special video for "Kaihouku". By adjusting the volume bar, you can manipulate the members performances in the video. When you put the volume at max, there is a scene where actor Nukumizu Yoichi makes an appearance. 

The members commented, "It's very fascinating and you can see many different worldviews, so we want many people to try it." 

Source: natalie, "Kaihouku" special website
Thanks to minlilin for the tip!