The Butler, In Sorrow and In Joy is Chapter 148 of the Kuroshitsuji manga.
All alone and carrying only one suitcase, Prince Soma wanders through London. He is approached by a little boy who recognises him as "Mr Curry Bun." The boy asks Soma why he did not hand out curry buns yesterday. Disheartened, Soma says that he cannot do this anymore. The boy then tells him under tears that he and his family—his mother and infant brother—are dependent on the weekly distributed curry buns and that they will starve without them.
Hearing the boy's words, Soma gives him his necklace. The boy thanks him, reminding Soma of Agni, before running to his mother and brother. However, when he arrives there, three thugs steal the necklace from the boy. From afar, Soma watches how the boy and his mother try, in vain, to get the necklace back and how the men then push the boy's mother away.
Afterwards, the thugs turn to Soma and demand him to give them something too. And when Soma tells him that he will not give anything to people like them, they attack him and take his suitcase from him. One of the men opens the suitcase and takes out Agni's urn. Another man suggests breaking the urn to see if any gold teeth survived the cremation process. The former one throws down the urn while the third thug holds back the struggling Soma who then snaps and kills the men.
Wordlessly, Soma gives the now bloody necklace to the boy before walking away, crying blood and cradling Agni's urn.