In a 2021 interview with Anime News Network, prolific Japanese voice actor Natsuki Hanae (who also voices Ken Kanecki in "Tokyo Ghoul" and Korai Hoshiumi in "Haikyuu!!") admitted that he and his fellow cast members almost lost their voices while recording "Demon Slayer: Mugen Train."
"I was concerned that everyone might lose their voices, since we all recorded with so much seriousness and intensity," said Hanae. "There were numerous battle scenes with lots of background noise, and Tanjiro had his voice raised the whole time. There were also many scenes where he was going through a roller coaster of emotions, so this time I prioritized showcasing those emotions in my acting."
Indeed, there are numerous battle scenes within the film where Tanjiro and his comrades are screaming from start to finish, especially in the climactic final battle between Akaza and the Flame Hashira Kyojuro Rengoku (Hiro Shimono). Following that battle, which ultimately ends in tragedy, the three main protagonists also start screaming and crying to mourn their fallen mentor — another scene that no doubt pushed Hanae's voice to its limit. In any case, it's clear that Natsuki Hanae went above and beyond to capture an intense vocal performance for "Demon Slayer: Mugen Train."
