One of the original plot threads teased when Fire Force first began was how Shinra Kusakabe survived a mysterious fire that took the life of his mother and brother when he was little. As he works with the Special Fire Force, Shinra has begun to get new details behind this event and it's increasingly become clear that an Infernal was at the root of the mysterious fire. But things are about to get more complicated as Shinra and his brother are about to cross paths. After finding out his brother was alive in a previous episode, Shinra will soon find out what this really means.
Episode 15 of the series began a new arc that will set Shinra on a direct path to clash with his brother, and with this comes the confirmation -- from the series' official Twitter account -- that Maaya Sakamoto will be voicing Sho Kusakabe in the anime going forward.
Shinra and the rest of Company 8 had their first official clash with the Knights of the Ashen Flame in the previous arc in which they played a big part in bringing confusion and destruction to Asakusa. This resulted in a pretty powerful Infernal that Shinra played a role in helping to bring down, and this has put him squarely in their sights.
Now they're aware that he was the "Devil" they were looking for, and this surprisingly includes his younger brother Sho, who's now a Commander of these mysterious knights. With Shinra and Sho on opposite sides, it's only a matter of time before their explosive fight. This is teased a bit in the new opening theme for the series, so it's probably going to be even more impressive in the official clash.
You can currently catch up with the series on Crunchyroll and FunimationNOW, and can also find it running Saturday evenings as part of Adult Swim's Toonami block. Fire Force was first created by Atsushi Okubo for Kodansha's Weekly Shonen Magazine in 2015, and has since been collected into several volumes.
Kodansha USA has licensed the series for an English language release, and they describe Fire Force as such, "Terror has paralyzed the clockwork metropolis of Tokyo! Possessed by demons, people have begun to burst into flame, leading to the establishment of a special firefighting team: the Fire Force, ready to roll on a moment's notice to fight spontaneous combustion anywhere it might break out. The team is about to get a very unique addition: Shinra, a boy who possesses the unique power to run at the speed of a rocket, leaving behind the famous "devil's footprints" (and destroying his shoes in the process). Can the Fire Force discover the source of this strange phenomenon and put a stop to it? Or will the city burn to ashes first?"