"Lobster" (海老, Ebi) is an extra chapter included with Volume 8.
After being called over to Bang's dojo, Saitama learns that Bang got a whole bunch of lobsters from his brother and needs someone to help him eat them. Genos complains about them being called out for something insignificant, and tells Bang to call someone else if he needs help eating leftovers, at which point Saitama tells him to stop, saying that they're only helping a lonely old man with his food problem. After Charanko arrives with the vegetables, they start preparing the hotpot while talking about a recent dojo hunter that has been attacking other dojo's. Saitama notices that there isn't any Nappa Cabbage, interrupting the conversation about the dojo hunter, which annoys Charanko. After seeing Saitama look bummed about the fact that there isn't any cabbage, Genos angrily asks Charanko why he planned to make hotpot without cabbage. Saitama tries to say that it's fine, but Genos keeps arguing with Charanko because he does not feel like he even feels sorry for not having bought cabbage. After Charanko challenges Genos to a match, Bang tries to calm down the situation by saying that he will go buy the cabbage, and asks Charanko to get along with the other two.
As they are preparing the ingredients, the dojo hunters from the Harsh Path Style came to challenge Bang only to find Charanko, Saitama and Genos cooking hot pot. Charanko tries to stand up to the dojo hunters and calls Saitama and Genos for help, but they began eating the hot pot. Charanko was then struck almost landing on the pot, before Saitama caught him with his chopsticks. When one of the dojo hunters notices the lobster, he tries to stomp them, only for it to be saved by Genos. Genos quickly pushes the hunter through the wall, while Saitama easily defeats the rest, leaving the dojo in ruins. Bang returns from the store, only to find his dojo ruined. He immediately blames Benpatsu, the last remaining dojo hunter.
Outside, the Harsh Path Style dojo hunters are walking back, talking about Bang's dojo, they encounter Garou who happened to hear of their conversation. Garou proceeds to beat every member and when asked about his identity he dramatically states to be "a villain".