Shemalecompanion E C Sites Single Szh 1 She Male Companion Manga with a male anti-hero

shinigamisama ni saigo no onegai o :
Aida Shizuka is three days from being executed for cruelly murdering his family when a shinigami comes to visit him. It's his little sister Hibiki, who has come to make sure his soul goes to hell! as she wants to be the one to get revenge, she makes him escape from prison...
the main character is not all he seems to be in the first chapter, it's really interesting. don't stop at the beginning!
region :
It’s February, and it still hasn’t snowed. Kanon’s father is going on a business trip and might be getting too friendly with a subordinate, which Kanon doesn’t approve of so soon after her mother’s death. Her little brother collects insects, but they’re dying off.
And it turns out that this die off is the first of many a plague to come down. First it’s the insects. Then it’s the rats, looking for a new food source. Then it gets bad…
a bit of gore in this one but the teacher is quite the character you're searching for (not the ugly bad teacher, the other one obviously). i like this manga a lot but don't read if you don't like gore.
warau kanoko sama :
Although she doesn't get along with people very well Kanoko considers herself a perfect "observer". Her hobby is observing the students in her third year junior high class and keeping a journal of the classroom drama. But what will happen when Kanoko becomes involved with some of her classmates?
it's a shoujo, and more centered around the girl, but tsubaki has the kind of character you describe, but i'm not sure if we see enough of him for you to be satisfied... still it's a funny, good shoujo.
ghost hunt :
mai's school is haunted. every time somebody try to tear down the old building, accidents happen. so the director engaged people to solve the mystery. among them is kazuya shibuya. and when mai get involved with him and his research by accident and end up working for him, she found herself in more trouble than she was bargaining for... and i mean it!
that guy character is a complete mystery! but he does seem like the kind of main character you're searching for...
eru arukon - taka :
historical manga set in 1580, at a time when fights over colonnies made england and spain ennemies. the main character is the son of an english man and his spanish wife. but he is actually the son of his mother and her spanish lover. he becomes an officer in the english navy, ready to do anything to get to the top, all the while planning to betray england for spain.
in this one the hero is actually bad, a anti-hero. he will do anything to get what he want, but he is so charimatic that i was completely hooked. the art is a bit old tho...
tower of god :
the hero has to climb a tower with trials on each floor to get what he wants.
maybe not the hero, though he IS ready to do anything to get to his goal, but his companion, koon, is very much like your description, he is not the main but he get more and more important as the story goes on...
that's all i can think of for now...
by the way i also love the art in "deep bloody night", it's a good pick

I agree with shinigamisama ni saigo no onegai o, other ones are:
-Bloody Cross
-Fukashigi Philia
-Infinity Game