Deca-Dence was a big hit in the Summer 2020 anime season. Initially, the post-apocalyptic monster-fighting anime drew Attack on Titan comparisons, with some labeling it a clone of the series. But those accusations didn't last long, disappearing when an early twist transformed Deca-Dence into something quirky, inventive and ambitious, garnering a large fanbase both in and out of Japan. Following the season finale, fans have been wondering whether a second season is in the works. The show holds the sentimental position of being Studio NUT's debut anime original, and it's become very popular. Still, even with everything in its favor, it's hard to say whether fans should expect any more Deca-Dence.
Cutting to the chase, a second season doesn't make a whole lot of sense. The anime original is certainly popular enough to warrant a follow-up, but its final episode doesn't leave much room for one. It settles on a note of finality, tying up major loose ends and ending the series in a satisfying way. That being said, a recent interview with director Yuzuru Tachikawa provides a little hope. Tachikawa said he is thrilled to see Deca-Dence reaching a large audience, and remarks he'd be open to a second season "if there's a way to express something new in a different format." Not overly promising, but at least it's not a straight-up no. It's worth noting that Yuzuru gave this interview before the final episode had aired, so that may have affected his answer.
Yuzuru was also asked how overseas fans could support a second season (apart from streaming the show legally, of course). Unfortunately, the anime industry is kind of oblivious to foreign audiences, though Yuzuru does mention that fan art, fan fiction and a general social media presence is nice to have.
Again, the very complete ending leaves no real need for a second season. Deca-Dence's popularity certainly warrants something, but there's no telling what that could be. Right now, an OVA, movie or spinoff series seem possible. There could be a slice-of-life excursion into the characters' lives post-episode 12, or even a Deca-Dence spinoff series set sometime in the past or future. As the show is an anime original, it isn't tethered to any source material. If Yuzuru and the show's writers want to whip up more Deca-Dence, they can do so at any time.
For now, it's probably best for fans not to get their hopes up. If there's no more Deca-Dence on the horizon, there's at least solace in the fact that the original series finished strong, which is a blessing nowadays. Also, as the Fall 2020 season approaches, the next seasonal hit is not far away.