I'll be honest here: I didn't finish the manga. I just read what the library had and didn't bother to finish it online. Not really worth it since it's one of the WORST manga I've ever read.). But, sadly, I read most of it. I just really want to voice my opinion about this series.
(Warning: There is some language and some spoilers.)

Story: 1/10
It's stupid, to say the least. I read it because it was there, but...ugh. I had low expectations, but the reality was worse. So, if you read the description, "Hot Gimmick" is about a girl who's 'forced' to become a rich guy's 'sex' slave. There are too many terrible cliches and unnecessary 'drama' throughout the series. But, I do admit, the side-story with Hatsumi's sister and their childhood friend was good and realistic.

Art: 3/10
The characters were ugly and too many time the backgrounds were pictures of actual parks and whatnot. It's lazy and awkward to see these characters stand in a 'real' picture.

Character: 3/10
I hate most of the characters. Hatsumi is retarded. I am not joking; with Lord knows how many times she's been abused (mentally, physically, and sexually), she doesn't do ANYTHING! We're supposed to like her because she forgives everyone and she's too nice. What a role-model...
Then there's Ryoki and Azusa. These two assholes are...assholes. Ryoki is abusive and constantly tortures Hatsumi to be his 'sex slave.' But it's okay because he loves her. BULLSHIT! Then the mangaka wants us to feel bad and like Azusa. He has a grudge towards Hatsumi's father and tries to get revenge by (attempting to) gang-bang her. Then we get into his 'sob-story'.
Hatsumi's sister is a user and an asshole (until her relationship with their childhood friend, she's okay then).
But I said "most." There are two notable characters: The childhood friend and Shinogu. Both are really nice and I feel bad that they're in this manga. The childhood friend (don't feel like looking up his name, sorry) is good throughout the series. But this damn mangaka WANTED me to hate my favorite character, Shinogu. She did this by having him crush on his sister. I mean, I respect how hard he tries to ignore this feeling, but THIS ISN'T NECESSARY!

Enjoyment: 1/10
Yeah.

Overall: 3/10
Overall, I hate the story, lazy art, and most of the characters; while the only redeeming qualities were the side-story and the two characters I mentioned above. My apologies for the poorly made review, but please stay awy from this series.