The story of Darker than Black: Ryūsei no Gemini begins several years after the epilogue of its prequel, Darker than Black. It is centered around one Suou Pavlichenko, a mostly ordinary teenage girl who lives with her father and twin brother, who got turned into a contractor two years earlier when he got hit by a falling comet. Her ordinary life is suddenly upturned one day when it seems that every intelligence agency in the world wants a piece of her, and she gets dragged off by Hei, the now even more apathetic main character of the prequel.
Like its prequel, Darker than Black: Ryūsei no Gemini has lots of action with someone invariably dying (or at least looking like they’re dying). And it’s not the cheesy sort of action, although one repeatedly recycled “magical girl transformation sequence” feels out of place. There is also no lack of intrigue. Unlike the prequel, however, the plot is narrowly focused, and there are no major side stories or fillers that deviate from the main plot. This makes for much more tighter storytelling.
On the other hand, the whole plot is basically a side story itself. Not much of the questions that remain from Darker than Black have been answered, and what little answers there were are outnumbered by a whole lot of new questions. In fact, one might not be wrong to think of Darker than Black: Ryūsei no Gemini as little more than setup for yet another sequel, even if the setup is fun to watch in its own right. Things can’t go wrong when there are characters such as a stoic lesbian who has to kiss men to maintain her powers. (OK, I may be imagining the lesbian part …)
Should you watch it? If you liked Darker than Black and can tolerate a lack of revelations, then you should. If you can’t stand even more questions being raised without many answers for existing questions, then you might be better off not watching it until another sequel ever comes out. If you haven’t watched Darker than Black or didn’t like it, then you probably won’t want to watch the sequel.