If you are interested in Japan, you've probably known about the Demon Slayer: Kimetsu no Yaiba. If you don't know about it but are still interested, check out Amazon.com and you'll see you can buy digital editions with ease.
Just to give you some background info, the Demon Slayer: Kimetsu no Yaiba is a Japanese comic that made a huge hit in 2020, in which the top 20 most sold comic ranking of the year was almost dominated by it (there are 23 volumes). Besides comics, there's a movie and songs that bolster the almost historical hit in its genre.
The protagonist is Tanjiro, a noble, benevolent young man whose family was slaughtered by a demon, except his younger sister, Nezuko, who survived the disaster but turned into a demon. Tanjiro's story centers on his effort to save Nezuko, hoping to find a way to turn her back into human. As the story develops, Tanjiro joins the demon slayer corps where he learns esoteric swordsmanship and masteries to kill demons.
No spoilers here, but to kill demons, you must decapitate them. Simply by that, the Demon Slayer may be rated R under the MPA film rating system in the US, figuratively speaking. I saw on TV a guy who said that the depiction of decapitation in the cartoon is too gruesome and too violent. Is it really so?
In the feudal era in Japan, there was a custom called "harakiri", or more officially, "seppuku", meaning stabbing the abdomen and kill yourself. Traditionally, human's soul is considered to rest on the abdomen, and stabbing there means directly attacking the soul and ending life. However, as you can imagine, harakiri involves grievous pain and IS a terrible experience because you will see your own guts burst out of the abdomen, needless to say lots of blood. Excessive bleeding is a slow, painful death.
Lucky enough, there's always a man standing behind you, carefully seeking the opportune moment. His sole role is to chop off your head. The timing is everything. He cannot miss. By beheading soon after you stab your abdomen, he literally finishes the pain. He is a well seasoned swordsman who can strike at the right moment without hesitation. The custom of "seppuku" is established, therefore, based on rectitude and benevolence.
In the Demon Slayer, demons used to be humans, but they became demons not because they were destined to be demons but because we all are fallible, weak, and corruptible. Readers consciously and unconsciously concur with such idea and reminisce themselves as such in everyday life. Tanjiro kills demons but, at the same time, shows empathy and compassion to decaying demons after being decapitated.
Demons often suffer from various misfortunes during their earlier lives before becoming demons. After they become demons, they forget pain and become invincible (again the ONLY way to kill them is to cut off their heads. No wounds can do much to them). However, inside, they continue to suffer from their past life.
Beheading will end demons' lives and, in a way, their suffering for sure. Tanjiro is skillful to perform such role and, at the same time, benevolent enough to feel sympathy for them, representing "bushi no nasake", according to Inazo Nitobe, the author of "Bushido: The Samurai Code of Japan", the tenderness of a warrior. Nitobe also says that "bushi no nasake" implies mercy where mercy did not remain merely a certain state of mind, but where it was backed with power to save or kill.
Beheading is as brutal and violent as it gets, but in the context of the Demon Slayer: Kimetsu no Yaiba, it means benevolence, indifferent and just, regardless of what you are.