How can I replicate art for the following anime/manga?
I don't think any tutorial in the internet has the following how-to guides for the characters in the series I want to replicate, so I guess you guys know how...

In case that isn't possible to find here in this forum, any of you guys here have ready or on-hand digital sources/art books to the following anime/manga I'm looking for?
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Anime/Manga series
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Nagasarete Airantou
Hidan no Aria
Campione!Matsurowanu Kamigami to Kamigoroshi
Isekai Maō to Shōkan Shōjo no Dorei Majutsu
Only a small handful of Japanese artists do art tutorials. I haven't seen anyone break down another artist's style and give tutorials for how to draw something their way. Most often, it's just a generic tutorial for how to draw a Bishoujo/Lolita, Chibi, or Moe style character.

If you want to replicate artists, like Fujishiro Takeshi, then the only thing you can do is copy, copy, copy his illustrations until you figure out the fundamentals of his style on your own. The way you're going to go about replicating his style will likely be different compared to how he goes about it. There's plenty of resources if you search for '描き方' and whatever style you want (i.e. 美少女, 萌え, etc.).

Fujishiro Takeshi (藤代健) Art Book: 藤代健イラスト集 藍蘭島絵巻
Tsurusaki Takahiro (鶴崎 貴大) Art Book: Private Garden 鶴崎貴大画集
@Taruby
Damn! (teary-eyed emoji) I wuz hopin' there wuz... (tears-flooding emoji)...

Wanted to do some "What If..." scenarios for those mangas with a kinky hentai twist...

My brain was flooding with ideas every time I see the scenes of the male main character sleeping or being alone with any one of the girls.

My lewd dark side especially was hot for "Hidan no Aria/Aria the Scarlet Bullet". Every time Riko Lupin gets lecherous with Kinji I was thirsting for scenes where they go all the way... (naughty smile emoji). Same goes for Ikuto in "Nagasarete Airantou" - I wanted a depiction of him go into Horny Harem Master mode and bang every supporting girl character hottie in the island's secluded areas... (lolling pervert tongue emoji)

In the meantime, I hope to run into an online library of art book scans from the info you gave me.

Damn, I hope there REALLY are some online - many hentai aficionados are waiting to have their perversity sated... (lolling pervert tongue emoji and naughty smile emoji)
mangaflea said:
@Taruby
Damn! (teary-eyed emoji) I wuz hopin' there wuz... (tears-flooding emoji)...

Wanted to do some "What If..." scenarios for those mangas with a kinky hentai twist...

My brain was flooding with ideas every time I see the scenes of the male main character sleeping or being alone with any one of the girls.

My lewd dark side especially was hot for "Hidan no Aria/Aria the Scarlet Bullet". Every time Riko Lupin gets lecherous with Kinji I was thirsting for scenes where they go all the way... (naughty smile emoji). Same goes for Ikuto in "Nagasarete Airantou" - I wanted a depiction of him go into Horny Harem Master mode and bang every supporting girl character hottie in the island's secluded areas... (lolling pervert tongue emoji)

In the meantime, I hope to run into an online library of art book scans from the info you gave me.

Damn, I hope there REALLY are some online - many hentai aficionados are waiting to have their perversity sated... (lolling pervert tongue emoji and naughty smile emoji)
youll need the settei, Settei (character settings/model sheets) are used as reference by animators when creating anime with notes from the animated character designers who simplify the sometimes too much complex designs from the manga for animation, of course only from the animated versions of such media, since the mangakas create their style organically it dosent exist a "how to" for the manga version of the characters design.

you can find some settei here plus the color palette sheet

https://setteidreams.net/settei/

and here is the settei for Hidan no Aria with character design, nude bodies, clothed bodies, expresions, locations and guns

https://setteidreams.net/settei/hidan-no-aria/