Tie-in ONA aren't like other productions. Rather than telling their own story, they have to promote a completely different one, often in an entirely different medium. Now, for what it's worth, Destiny Child does this. I can't say how well or not it attracted me to the franchise, being as I had briefly played the game long before watching, but it did manage to introduce the story, characters and world to a reasonable degree.
That being said, it doesn't excel anywhere at all. Despite the premise having potential, without being given the reigns to a full story there isn't any room to really use it. The same is true for the concept of the Children (the given plural is Childs, I should note), who again aren't used to any interesting extent. So without anything being pushed to be impressive, the whole ONA ends up quite mediocre.
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As mentioned, the story has some decent material, but there isn't any progress with it. Nigh all of the plot is delivered either via exposition or fighting, with the latter having practically no stakes, as it is never clear how many Demons or Children are present nor are any rules regarding the combat established. As for how the story is conveyed, the bulk is dedicated to the character arc of and navigated by the Deuteragonist. I wouldn't say this is explicitly an issue, but if told through the actual Protagonist then a lot more of the lore and mechanics could be explored.
The characters are just vacant. Only the two leads have any kind of personality, and even then their arcs are pretty vague. Everyone else is one-note at best, and several don't even get a single line yet are significant enough to be named. For as much as it is later set up that Children reflect various aspects of their sources, this concept is extremely lightly used, despite granting many opportunities for interesting dynamics.
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While the designs are great, with almost all being quite memorable, the artstyle itself is almost repugnant. Noses and cheeks are super red and shiny, a style that I personally detest. Animation has no problems, the effects around hiding the Demons and their Channel Evil were pretty neat, but nothing else really stands out. The music is listenable but not at all memorable, and there is no OP to speak of, only an ED, which is again alright but not notable.
Little is seen of the Demon world, but the limited amount shown is quite interesting. The landscape near the end is particularly striking, and a neat departure from common interpretations. As for the tone, I couldn't really pin anything down, which goes for the themes as well. And finally, as for the miscellany, I thought that the unique contract styles of different demons were interesting, as was the second shown Child transformation sequence.
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All in all, Destiny Child is just a short, inconsequential ONA with nothing particularly special going on. It could likely be improved just by delving more into the plot, but that would probably make it into a direct adaptation rather than a tie-in. Aside from that, the overall concept could be retooled into a different franchise, but again that wouldn't be an improvement more a replacement.
I wouldn't go so far as to say it's an absolute waste of time, but it's certainly skippable.
