Okay, this is gonna be a super long comment, so apologies in advace. So, as you may know, anime is pretty much the animation industry in Japan which can be presented in seasonal TV series, long running weekly series (not that common anymore, but very popular back in the day), featured films, etc... Manga are the comics of which a majority of anime are based off of, but there is also a smaller percentage of series that are based on light novels; and an even smaller percentage based on web novels, visual novels, webtoons, games or be completely original content. Most of these media are not exclusive to Japan, but the vast majority of anime's source material is from Japanese origin, followed by some anime that adapt Korean comics (manhwa) and light novels, then some small percentage of Chinese comics (manhua) and light novels and an even smaller percentage of other countries' stuff, some recent examples being the Scott Pilgrim anime adaptation, Cyberpunk Edgerunners, or even the Suicide Squad anime which is airing this season, all made by very popular Japanese animation studios. As far as Demon Slayer goes, it is a very popular series that started airing in 2019 and has since released a season, a movie, 2 11-episode arcs and a 8-episode arc. This trilogy of films that was announced right after the end of the latest arc will adapt the Inifnity Castle arc, which is the second to last arc of the series. In terms of recommendations, there are some creators on RU-vid like arikendo, who goes into detail into some of anime's general concepts like animation studios, genres, tropes, etc... I also recommend some of Gugguk's seasonal videos as he gives a quick summary of the first episode(s) of whatever is airing on the current season, so you may find something that you want to watch. Some of his best videos are also his yearly "best of anime" videos which will obviously be filled with awesome recommendations. And he also has some good videos where he gives other general recommdations. Some of my personal recommendations: Some action series: - Demon Slayer - Jujutsu Kaisen - One Punch Man Some more serious stuff: - Attack on Titan - Vinland Saga - Death Note - Full Metal Alchemist Brotherhood The "Big 3": - One Piece - Naruto - Bleach There's so much more that anime has to offer, but these are just some very popular series that usually get people into anime. It is also worth noting that anime has a ton of genres and subgenres catering to all types of demographics, but that's pretty much for you guys to discover.
