Sena released a warrant arrest to Kazuma due to sabotage a governor's mansion. Kazuma tried to oppose of allegations against him as well of his party and fellow adventurers who defended him, but failed due to Sena will set charges against who joined during the incident.
This Episode is adapted from volume 3. Some of the key differences include:
In the Light Novel, Dust also got arrested on purpose, because he wanted the warm food and shelter at the jail. The Anime adaption excluded this.
In the Light Novel, Kazuma threatened Aqua with revenge for how she only tried to save herself during his arrest. Because of this, when Aqua arrived at the jailhouse with ill-planned jailbreak schemes, she explained that they already planned to help him, and "NOT because she feared his punishment later." (an obvious lie)
Megumin likely knew Aqua's jailbreak plans will fail, but she will go along with any and all plans that allowed her to use Explosion.
The Light Novel version of Sena has a much more serious demeanor, and did not do the various poses during the trial.
While the Light Novel hinted that the trial is rigged and Alderp planned to have Kazuma executed from the start, the Anime took the concept way further and had executioners prepared and ready in the background.
In the Light Novel, Aqua tried to "help" at Kazuma's defense trial, using what she learned from video games like "Based Attorney" and "Manganronpa." In the Anime, Kazuma was largely spared of Aqua's meddling.
In the Light Novel, the Judge and Sena altered their judgments at the end in a very awkward manner, as if some supernatural presence altered their minds. In the Anime, Alderp simply forced the Judge to change Kazuma's sentencing.
In the Light Novel, Darkness first revealed her high noble status towards the end of the trial in order to save Kazuma. In the Anime, they already revealed her nobility status in Season 1 Episode 10.
In the Anime, a group of Knights came to the party's mansion and confiscate everything of value. In the Light Novel, that was implied, but never shown.