Koshfa

The overall style of the manga seems to be mostly inspired by illustrations from old fairy tales

(Household stories from the collection of the Bros. Grimm 1922)

But Kamome combined this Fairy Tale style with elements from many other styles, for example:

-Art Nouveau

("Zodiac" by Alphonse Mucha 1896)

("illustration for Le Morte Darthur" by Aubrey Beardsley 1893)

-Baroque

("A New Book Of Ornaments With Twelve Leaves" Matthias Lock and Henry Copland, 1752)

- Rococo

("The Apotheosis of Hercules" François Lemoyne 1736)

-Western Comic Style

The western style should come as no surprise since Kamome did work for DC Comics