Let's Meet in a Nightmare is the sixth Katekyo Hitman Reborn! Drama CD to be released. The story details when Tsuna's and Mukuro Rokudo's dreams are somehow connected, and Mukuro decides to mess around with Tsuna's dream.
Reborn wakes up Tsuna since he was talking in his sleep and immediately threatens him not to make any noises while sleeping, much to Tsuna's horror, and Tsuna promises that he wouldn't do it again. Reborn then asks what kind of dream he was having, but since Tsuna couldn't remember a thing, Reborn tells him to prepare and go to school.
When Tsuna arrives at the school gate while mumbling about Reborn's treatment this morning, he accidently bumps into Hibari, and immediately apologizes. Hibari then asks if he was with Reborn, to which Tsuna answers that he wasn't. Hibari then tells him to ask Reborn when he could fight Mukuro again. Tsuna remembers that Reborn has promised Hibari that he could fight Mukuro again in exchange for participating in the Ring Battles. Tsuna assures Hibari that he would tell him later. When Tsuna was about to reach the classroom, Yamamoto approaches him, making Tsuna asks why Yamamoto was outside the classroom. Yamamoto points at a group of girls gathering outside their classroom and Tsuna notices that Gokudera was in the middle, flirting with them, much to Tsuna's shock. However, when Gokudera approaches Tsuna, Tsuna quickly realizes that he wasn't Gokudera, but Mukuro possessing Gokudera's body. Mukuro muses at Tsuna's Hyper Intuition and comments that he thought that he had played Gokudera's role pretty well, but Tsuna responds that Gokudera was nothing like that. Tsuna questions Mukuro why he was possessing Gokudera's body, to which Mukuro answers that he was bored and decided to take a stroll to kill time as well as to gather information about Tsuna and his Guardians, reminding them of his hatred for the mafia and his desire to destroy the Vongola Famiglia. Tsuna shouts at him to leave peacefully, but Mukuro refuses, saying that he wanted to enjoy outside world a bit longer, and decides to possess another body. He then leaves Gokudera's body as he challenges Tsuna to find him.
After school, Gokudera let out his frustrations and annoyance at the thought he was possessed by Mukuro a while ago. Tsuna and Yamamoto tries to comfort him, but fails when Yamamoto mentions that his popularity among the girls in their class will rose. Tsuna then thinks who Mukuro will possess next. Gokudera then reminds the battle at Kokuyo Land, making Tsuna realizes that his next target would be either Bianchi or Hibari.
At the school front gate, Mukuro, who's possessing Bianchi's body, notices Hibird singing the Namimori Middle School Anthem before calling out Mukuro's name, much to Mukuro's astonishment. Hibari then approaches Mukuro, unaware that he possessed Bianchi's body and questions why he was at school. Mukuro replies that he comes to see Gokudera. At this time, Tsuna, Gokudera, and Yamamoto arrives at the front gate and get confused which one who is being possessed by Mukuro until Reborn arrives. Tsuna immediately realizes that it's Bianchi who is possessed since Bianchi would normally get excited whenever Reborn is around. Mukuro then leaves Bianchi's body and asks Tsuna if he could he find him again. Tsuna thinks in panic where Mukuro is as Mukuro's signature laugh is heard, until Tsuna can't take it anymore and yells at Mukuro to stop.
When Tsuna opens his eyes, he finds himself in a field, and Mukuro in front of him. Mukuro explains that what he experienced before was nothing but a dream. He says that his and Tsuna's dream was somehow connected, so Mukuro decided to use the opportunity to provide some entertainment for Tsuna and asks did he enjoyed it, to which Tsuna protests that he didn't and shouts at him to get out from his dream. Mukuro tells him that he would have done so even without him telling him to, as his body was already at its limit. Before Tsuna could ask further, Mukuro disappears as he tells Tsuna that once he wakes up, he would forget everything.
Tsuna abruptly awakes from his sleep, thinking that it was all just a dream. Before he could think further, Reborn shoots a bullet at him, telling him not to talk in his sleep. Tsuna quickly apologizes and falls back asleep. The story ended with Mukuro's voice telling that they should meet again next time not in a dream, but in reality.