WARNING: This review will feature spoilers for the characters and plot of this movie. Read at your own discretion.
~~~This film is very impressive in terms of its visuals and animation quality, however it is ultimately middling at best.
The plot of the film does not justify its nearly two-and-a-half-hour long runtime - in fact, the first half of the film could be significantly cut out without affecting the events of the second half. In terms of how the film treats previous plotlines and established characters, it feels somewhat disrespectful toward its predecessor Space Battleship Yamato: The New Voyage as it squanders the potential of two characters introduced in that entry of the franchise. At first developments in the second half appear to give depth to the antagonists of this film duology, but then further twists scuttle those ideas and, in the process, create plot holes for this film's narrative. Overall, this film's story is in my opinion filler in the sense that a watcher of the Yamato/Star Blazers franchise could skip Be Forever Yamato and move onto season 3 of the television serial without experiencing any confusion as to how the cast ended up where it is in that series.
~~~As far as the characters unique to this film are concerned, only Alfon is interesting to any extent, and he is sadly not
that interesting to watch due to his minimal contributions to the overall plot beyond attempting to romance Yuki. He may have been more memorable if he had defected to the heroes' side or made the audience sympathize with Black Nebulans, but instead he takes up time trying to seduce Yuki in a subplot that feels wholly unnecessary due to Yuki's unwavering devotion to her boyfriend Kodai rendering his efforts a failure before they even began.
Mio Sanada, on the other hand, is even less interesting than Alfon due to being a copy and paste of Yuki who doesn't get time to display a different personality before unceremoniously dying in a sacrifice that was utterly unsatisfying given that it stops her from contributing further to the Yamato franchise and retroactively made the last film a pointless addition to the series.
Before ending this section, I would also like to address the matter of Captain Yamanami. This character is visually a reskin of Hijikata from the Comet Empire arc but unfortunately has neither the character of Hijikata nor Okita due to his limited screen presence. If the film had Kodai serve as the captain of the Yamato the entire runtime as he did in
The Comet Empire and
The New Voyage absolutely nothing would be different without Yamanami's presence.
In short, this film has some beautiful backgrounds and animation effects during its battle scenes (it's especially pretty in the second half), but its less than compelling plot and bloated runtime make the viewing a very "mid" experience in the opinion of this reviewer.
