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——!? -
Type: ONA
Episodes: 1
Source: Game
Genres: Action, Fantasy
Studios: Studio Hibari, Ultra Super Pictures
Producers: XFLAG
Duration: 8 min
Rating: PG-13 - Teens 13 or older

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)