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