In commemoration of the live appearance of the Haitoku Pistols at the XFLAG PARK 2017 held at Makuhari Messe International Exhibition Hall, a pseudo sequel to Mon-Soni!: Senritsu no Lucifer, Tada Hitotsu no Hajimari no Uta was created and posted to Monster Strike's official YouTube channel. The Haitoku Pistols meet at the cafe and talk about the event after looking at flyer of it. (Source: MyAnimeList)