Manga with Asexual Characters

So I've been doing some digging to find some asexual manga or characters. Not all of them are canonly asexual, but they have shown signs of possibly being asexual.

One Piece by Oda Eiichiro

• Enter Monkey D. Luffy, a 17-year-old boy who defies the standard definition of a pirate. Rather than the popular persona of a wicked, hardened, toothless pirate who ransacks villages for fun, Luffy’s reason for being a pirate is one of pure wonder; the thought of an exciting adventure and meeting new and intriguing people, along with finding One Piece. Following in the footsteps of his childhood hero, Luffy and his crew travel across the Grand Line, experiencing crazy adventures, unveiling dark mysteries and battling strong enemies, all in order to reach One Piece. Luffy has no interest in men or women; his only love is the love for adventure.

​Self by Saku Yukizou [NSFW]

• Self follows the story of a man named Youichi. He has a regular sex life, however he is not at all interested in sex, finding it much like a chore. After picking up a book called "Masturbation" he becomes interested in the concepts that are in it and starts to "experiment" with them. NSFW because lots of sexual content. 

Black Cat by Yabuki Kentaro

• It's about the infamous former assassin Train, better known as Black Cat. After quitting he takes on jobs as a bounty hunter, until his past begins to catch up with him. This manga doesn't deal with anything sex-related, but the main character has shown signs of being asexual. He was always quick to say that his best friend (who is a female) is nothing more than a friend, and that he has no sexual desire for her or anyone else.

​Medaka Box by Nishio Ishin

• Medaka Kurokami is elected as Student Council President her first year of high school. Since she was just elected she was given all of the Student Council's responsibilities. Overwhelmed by all the work, she asks her childhood friend Hitoyoshi Zenkichi for help. This manga isn't really my cup of tea because I feel the characters are over-sexualized, but I've heard at one point in the manga the main character, Medaka, is shown to be openly asexual, not caring for relationships or sex. Her friends eventually accept her asexuality.

​Shuuseki Kairo no Himawari by Mihara Mitsukazu [NSFW]

• Specifically talking about the first short story in this series: Keep Those Condoms Away From Our Kids. A tale about kids that have completely lost their sexual desire. NSFW because of nudity and sex.

​Gekkan Shoujo Nozaki-kun by Tsubaki Izumi

• Nozaki Umetarou a tall, handsome, and somewhat intimidating high school boy and the object of Sakura Chiyo's affection. However, after Chiyo confesses to Nozaki, he believes that she is just a fan of his popular shoujo manga. One misunderstanding leads to the next and before she knows it Chiyo ends up working for Nozaki and aids him in making monthly girls' romance manga. Even though Nozaki is the creator of such a popular romance manga, he has absolutely no experience with romance and has no attraction towards females or males.

Death Note by Obata Takeshi

• An overachieving 12th grader, Yagami Light is an aspiring young man who seems destined for success. Unfortunately, his daily habits bore his incredible intelligence--So when a strange black notebook falls from the heavens during his class, it isn't long before he takes it for himself. In his room, he finds, to his horror/fascination, that the Death Note is real, and owned by Ryuk, a Shinigami. Any person's name written in the Death Note will die in 40 seconds without fail. With this supposed gift of God, Light swears upon his grave that he will 'cleanse' the world of the evil and needless people that inhabit it, thus creating a utopia for all. Light has been shown countless times in the manga as manipulative and uncaring for people. He seems to be incapable of loving. The antagonist, L, may also be asexual, expressing a love of sweets more than people.

​Durarara!! by Narita Ryohgo

• Ryuugamine Mikado is a boy who seeks for the exciting life of the big city, who yearns for an irregular life; a hoodlum, a stalker denpa-girl, an informant, a champion fighter, a black-market doctor, and the Headless Rider astride a black motorcycle. But despite how different they are, all of these stories are interconnected by mysterious incidents going on in Ikebukuro: mysterious kidnappings, a pharmaceutical group supposedly performing human experiments, and the mysterious "colorless" gang known as the "Dollars." From then on, the existence of supernatural cases and a gang called the Yellow Turbans will rise to the surface, and Ikebukuro will pushed to the breaking point. One major character in particular stands out as possibly being asexual: Izaya Orihara. In the novel, Izaya states that he is not attracted to any individual.

​Beelzebub by Tamura Ryuuhei

• Oga Tatsumi is a first year in Ishiyama High, a school for delinquents. One day while resting by a river he sees a man drifting along the current. Oga pulls the man to shore, who then splits in two and reveals a baby boy. The child turns out to be the son of the demon king, and Oga was chosen to raise it with help from the baby's demon maid, Hilda. Oga has shown to possibly be asexual; he is shy and tends to avoid becoming involved with romance.

Kuroko no Basket by Fujimaki Tadatoshi

• Kuroko is a member of Japan's legendary middle school basketball team, "The Generation of Miracles," and, while nobody seems to know about him, the main five players of the team all admit that he is a better player. When he joins the high school basketball team, everyone is surprised to find out that he is small, weak, and easy to miss. What is the secret that makes him so strong, and how will he help his high school team? Kuroko has been shown to be indifferent to romance and sex or unaware of attempts when people try to swoon him, as it is seen whenever Satsuki Mamoi attempts to infatuate him.

​La Corda D'Oro by Kure Yuki

• Every few years, the prestigious Seiso Academy holds a prominent musical competition, and only the very best students at the Academy are allowed to participate. Though all are eligible to apply, only students from the music department actually make it to the competition. Hino Kahoko attends Seiso Academy, though she is in the regular department and knows nearly nothing of music. That is until one day, when she meets a curious little creature who introduces himself as a music fairy by the name of Lili. Lili gives the unwilling Kahoko a magical violin, a violin which anyone is capable of playing. That day, the names of the students who are to participate in the music competition are announced – and Kahoko's on the list! Suddenly Kahoko is thrown into a world of music, where every note counts, and where she must strive to be perfect. One character in particular stands out as possibly being demiromantic: Len Tsukimori. He shows no affection towards anyone until later on in the story, where he develops feelings for Kahoko only after they become very close.

That's all I have for now. I didn't want to mention the obvious Haruhi from Ouran Highschool Host Club and Lelouch from Code Geass, who can also debatably be called asexuals. Black Cat is kind of like those so I dunno, not many people mention it which is why I added it in. The same kind of goes for Medaka Box, however it's more suggested that Medaka is asexual than the other three. If you have any more manga, feel free to add them in!