Non-Human X Human
Manga
some kind of romantic relationship between human and non-human (yokai girl, monster girl, vampire girl, alien girl, ghost girl, demon girl, etc). Non-Human X Human Part II is coming
Ane Naru Mono
The Elder Sister-Like One

Manga, ? vol, 2016
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Author:9
a boy summoned a demon girl to be his big sis
Hachigatsu Kokonoka Boku wa Kimi ni Kuwareru.
August 9 I Will Be Eaten by You

Manga, ? vol, 2020
Me:-
Author:9
a boy who is loved(stalked) by so many monster girl
Chotto dake Ai ga Omoi Dark Elf ga Isekai kara Oikaketekita
Yandere Dark Elf: She Chased Me All the Way From Another World!

Manga, ? vol, 2021
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Author:-
Kuchi ga Saketemo Kimi ni wa
Even If You Slit My Mouth

Manga, 11 vol, 2020
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Author:-
a boy with a slit mouth woman (kuchisake onna)

Manga, ? vol, 2018
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Author:9
a boy with a slit mouth woman (kuchisake onna)

Manga, 7 vol, 2018
Me:-
Author:9
a boy with a spider girl

Manga, 3 vol, 2009
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Author:7
isn't it obvious looking at the title, a boy has a cat and the cat can transform into a woman
Ookami to Koushinryou
Spice & Wolf

Manga, 16 vol, 2007
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Author:7
a man found a harvest god that turns out to be a fox girl
Rosario to Vampire: Season II
Rosario+Vampire: Season II

Manga, 14 vol, 2007
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Author:8
boy with a harem of monster girl
Rosario to Vampire
Rosario+Vampire

Manga, 10 vol, 2004
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Author:-
boy with a harem of monster girl
Negai wo Kanaete Moraou to Akuma wo Shoukan shita kedo, Kawaikatta node Kekkon shimashita: Akuma no Niizuma
I Summoned a Devil to Make My Wish Come True, but I Got Married Because It Was Cute.: Devil's New Wife

Manga, ? vol, 2020
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Author:-

Manga, ? vol, 2022
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Kagakuteki ni Sonzai shiuru Creature Musume no Kansatsu Nisshi
Creature Girls: A Hands-On Field Journal in Another World

Manga, ? vol, 2017
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Author:-

Manga, ? vol, 2021
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Author:-