I'm looking for a manga (or novel) which has in-depth & thick fantasy/supernatural setup/elements. No battle (little to none at all) nor power-level stuff. Alice in Wonderland imprints (or inspired by it) are not allowed! And the protagonist should be as humanely as possible (or not, depends on the narration). Some good examples are: Mahou Tsukai no Yome, Jinrui wa Suitai Shimashita (Novel), Mushishi, general Touhou stuff (the official ones).

Suzumiya Haruhi no Yuuutsu (Novel) While it is not technically a fantasy series but it has heavy and rich supernatural elements being shrouded underneath it. And crazy stuffs always happen around Kyon with or without him knowing.

Also, just like usual: Yuri, Yaoi, Shonen Ai, Shoujo Ai; are not allowed.

So I love, love, love well built fantasy/supernatural worlds so here are a few that are just lovely:

Ran to Haiiro no Sekai (Complete)
xxxHolic (Complete, just don't be too mad/disappointed in the ending...)
Majo (Complete)
Suiiki (Complete)
Omoide Emanon (Complete)
Children of the Sea (Ongoing)

And if you don't mind venturing into webcomics (and I mean comics published on the net and not webtoons/manhwa) then you should definitely take a look at Unsounded.

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Must Read Webcomic:
Unsounded

Lists:
Reading
Complete
Western Webcomics

The Voynich Hotel
Witchcraft Works
Kekkon Yubiwa Monogatari may be battling later on...