The "Day 13" episode will contain three stories. The first story, "Toki no Asase" (Shoals of Time), will center on Nero and Vanno persuading Frate to skip mass with them and see the circus. 

The second story, "Subete no Kinou" (Yesterday Before Everything), will focus on Ganzo, as he meets a young man named Vincente at a bar, and asks Ganzo to do something for him. 

The third story, "Ashita, Mata Ashita" (Tomorrow, and then Tomorrow), is set after Nero and Avilio defeat Mad Mack and are on the way back to Lawless. Nero suffers from fever dreams, and Avilio nurses him back to health.
 
(Source: Anime News Network)