TL:DR: Yakusoku is a great addition to the BanG Dream! franchise for those already familiar with the story of Roselia, but those who have only experienced the franchise through the anime may be left confused.
As the name makes clear, this movie focuses entirely on Roselia. Fans of BanG Dream will be familiar with this band already as they appeared heavily in Season 2 and 3 of the anime and are one of the main 4 bands in the franchise.
The movie focuses on the band story from Girl's Band Party, the rhythm game for mobile devices. It covers the first 2 Band Stories for Roselia and the Noble Rose -Bearing Flowers- event's story.
As a fan of Roselia and an avid player of the rhythm game I found myself highly enjoying this movie, however I can definitely tell how someone less familiar with the stories within the game would find themselves confused.
Band Story 1 especially ends up having a lot conveyed through a montage that doesn't really indicate too well what is actually happening unless you're already familiar with the story of the game, however I don't feel like it retracts from the overall enjoyment too much as the most important parts are covered very well (namely the formation of the band). Band Story 2 gets much better treatment, with pretty much all of the events leading up to the creation of the song "Neo-Aspect" being adapted very well.
The usage of the story from the event Noble Rose -Bearing Flowers- is a very nice addition, as that story is one of the better ones from the game and sees to the creation of one of Roselia's best songs, Yakusoku (Promise). It also gives confirmation that the song was written by Lisa, which was always implied but never canonically confirmed to be the case, which is welcome.
The animation is excellent, using full CGI animation for the characters as has become a staple in the franchise. SANZIGEN, who were responsible for BanG Dream! Season 2 & 3 as well as D4DJ First Mix return to do the animation and you can definitely see a huge improvement of quality from the earlier BanG Dream! works, with more expressive characters and detail in the animation. One thing that particularly stood out to me was the opening shots, which shows Lisa preparing for school in a classic "finishing getting ready" scene that almost every school anime has at least one scene of. This stood out to me not because of the content but the fact that it in CGI, a feat that I assume is much more difficult than with classic hand-drawn animation.
The OST is, as expected, amazing. The Opening and Ending songs are both new original songs by Roselia, Proud of oneself and OvertuRe, respectively. Background music is appropriate and pleasant to the ears and the insert songs are, of course, great. When Roselia is practicing, you can tell the songs were re-recorded to sound less professional and more like an actual practice session which is definitely welcome as a lot of music anime in this vein just play the studio versions of the songs and try to pass them off as practice. The real standout is of course Aiba Aina as Yukina, her vocals are still as incredible as ever.
BanG Dream! Episode of Roselia I: Yakusoku is a great movie for fans of the franchise that gives some of the better stories from the game in animated style, with a bit of a rewriting to fit the format. Even if you've only watched the anime seasons of BanG Dream! and are unfamiliar with the game, check this movie out. You may be left somewhat lost mid-way through but the experience is worth it, and who knows, maybe it will make you want to get more involved with the franchise and hop into the mobile game.
