Living with Monster Girl

Living With Monster Girl (also Living with Monster Girls and My Life With Monster-chan, among others) is a series of short, Doujinshi Hentai comics. The series revolves around a group of brothers, all identical-looking, who each have a relationship with a Cute Monster Girl of a different species. Each comic discusses not only sex, as is to be expected of Hentai, but also the trials and tribulations of each brothers' Interspecies Romance, the ways in which the couples sacrifice things for one another, and, well... their daily lives.

The single-page strips quickly gained fame through the Internet--specifically, Image Boards--for being remarkably sweet and touching (as well as funny) for being, well, porn. They're as much about the interactions of the couples as they are about the sex (in some cases, the majority of the comic is focused on the relationship over the sexual stuff). Oh, they're still NSFW, but in a cute way.

A spinoff Eroge based on "Living with Lamia" is also in the works.

Tropes used in Living with Monster Girl include:

Anime Anatomy: The front shot we get of naked Harpy in "Life with Harpy 2" is flat as a Barbie doll. Yes, in a hentai comic.
Blob Monster: Slime.
Breast Expansion: Slime's breasts seem to change based on her water and protein intake.
The Cameo: Slime shows up in the first panel of "My Life with Harpy."
Cute Monster Girl: More or less, the entire reason for these comics' existence.
- Arachne, however, pushes the limits of "cute" somewhat. She's got six eyes and claws!
A Date With Rosie Palms: This is more or less the only sex in "Living with Dullahan," as Dullahan's body gets naughty while her head is taking a bath.
Doujinshi
Ensemble Darkhorse: Lamia, from the looks of things. She's the girl getting her own spinoff.
Eroge: Based on "Life with Lamia."
Fetish Fuel: There's a monster girl to suit every taste, it seems.
Giant Spider: Arachnophobes are probably better off avoiding the two "Life with Arachne" comics.
Hentai
Image Boards: This was how the series became known, both in its homeland and in the West.
Losing Your Head: Poor Dullahan's head...
Make-Out Kids: Minotauros and her boyfriend have a tendency to get frisky when deliverymen come, if their comments are anything to go by.
Mermaid Problem: Living with Mermaid, as one might imagine. We never actually get a front view of the act, so we'll just have to keep guessing.
Naughty Tentacles: Lamia's tail has many... interesting applications.
No Guy Wants an Amazon: Harpy's boyfriend is just a little creeped out by the mental image of her completely ripped.
No Guy Wants to Be Chased: Averted in "Life with Mermaid:"--one of the things her boyfriend likes about her is how assertive she is in the water.
Petting Zoo People: Minotaur does not have a cow head--just some horns and cow ears.
Plot With Porn: Sometimes flagrantly. "Living with Dullahan" has only an (armor-obscured) Date With Rosie Palms, and everything else is about Dullahan's poor head not staying on right.
Squick: Harpy's boyfriend doesn't get why she eats her own eggs.
"You don't seem human girls sympathizing with their unfertilized eggs."
Tear Jerker: "Living with Lamia 1" is actually rather sad. Lamia needs lots of warmth in the winter, or else she hibernates. It's clear how lonely her boyfriend is when this happens, and while she gives him free reign, If You Know What I Mean, when he does, it's clear how empty it is.
Thanks for the Mammary: And Centaur's boyfriend wonders why she doesn't like him riding her. And not in the If You Know What I Mean way.
Training Montage: For a 6-hour sex session. It Makes Sense In Context.
Twenty Four Hour Armor / Living Armor: It's not clear which Dullahan is. Her boyfriend merely says she can't take it off, but it seems to be empty when her head isn't in it.
Two-Person Pool Party: Mermaid and her boyfriend go one better and have sex under the sea. While he's wearing diving equipment over most of him, mind...
Unusually Uninteresting Sight: Monster girls in general in this series.
The Woobie: Slime's situation is played for laughs, but it's kind of sad. She needs to bathe in fresh water every week, or she'll die. And if she and her boyfriend have prolonged contact, she starts dissolving his skin.