Monster Strike: Zoku Saishuu-banashi - Pandora no Hako
English title: An Encore and Continuance: Pandora's Box - A strange phenomenon is overtaking the world?! -
Japanese title: パンドラの箱 - 新たな世界のはじまり——!? -
Alternative titles: An Encore and Continuance
Type: ONA
Source: Game
Episodes: 1
Status: Finished Airing
Aired: Dec 31, 2016
Duration: 8 min
Rating: PG-13 - Teens 13 or older
Studios: Studio Hibari, Ultra Super Pictures
Producers: XFLAG
Genres: Action, Fantasy
Themes: Video Game

After defeating the War Gods, Ren and his friends are living the dream. 
It seems like they've finally managed to regain their normal lives. However, a mysterious girl by the name of Pandora appears, bringing with her a box that must never be opened. 
An unfortunate incident results in the box opening (of course), setting the world up for some big changes...

(Source: YouTube, edited)