In the Anywhere But Here series:

V.1 - Yama e Iku
? Yama e Iku (Going to the Mountains)
It's about a sensitive writer with an overactive imagination and intolerance for the banalities of everyday life.

? Yanagi Ki (The Willow Tree)
A woman stands day to day under a growing willow tree and watches the people who pass by...

V.2 - Sphinx

V.3 - Haru no Ogawa

The Poe family has to suffer the thirst for blood, as they live for eternity. They see loved ones die around them, and cannot be treated like normal humans, and have to live in fear as they may be killed if the humans find out about their existence. Having emotions of humans, and thirst for blood, why do such creatures live on Earth? A teenage boy from the family matures as he sees the cruel world around him.

Beautiful story. Very serene.

It's about a woman, a tree and a man and a life passing by.

This story shows that you don't always need a lot of words and that manga art can be as strong as any other style!

Mira attends a private school in England and finds out that the boy who appears in her dream since her childhood really exists. He's Radley Macchiavelli, a beautiful model. When the two finally meet, the boy is transported to a parallel world connected from one spiral ("Rasen"). Mira follows him to try to save him and is swallowed into the parallel world dominated by the mysterious Black King...

A man returns from a trip after hearing news about his former love's passing.

A young man is being used as a guinea pig in a mysterious experiment…

Conjoined twins Yudy and Yucy are as different as possible. Older Yudy is intelligent but ugly, as her nutrients are used up by her beautiful but simpleminded sister Yucy. Loving and hating so deeply, where does one girl begin and the other end?

From The Pink Panzer:

In the year 2999, only eleven cities still survive on Earth. The climate has changed drastically, and a biochemical apocalypse has made women extinct. For centuries, the male population of Earth has survived by depending on only one woman, called the Holy Mother, whose ova are harvested to create genetically engineered children. By now, any concept of a world in which women exist as ordinary people is long gone. Society has re-structured itself around all-male families, and gay relationships have become the norm.

At the beginning of Marginal, the Holy Mother is assassinated by a terrorist known as Grinja. The government in power doesn't want to start a mass panic, so it pretends that the Holy Mother has only shed her vessel, and that she will be miraculously "reborn" in the near future. The public, which is superstitious and devout, believes this easily. Only government officials know that behind the scenes, there is a frantic effort to create a new being with an XXY chromosome -- a male capable of giving birth. (This is a BL misrepresentation of an actual phenomenon known as Klinefelter's Syndrome.)

The manga's story revolves around one such boy -- Kira, the product of a genetic experiment, who becomes involved in a three-way relationship with Grinja, the aforementioned terrorist, and Ashijin, a young man who calls himself Kira's owner. A complex plot and flawless world-building make the story irresistible, and Kira's search for freedom is as symbolic as it is gripping.

The second shounen-ai manga ever published, The November Gymnasium focuses on chaste, yearning love between boys at a prestigious German boys' school.

The elite Cosmo Academy attracts applicants from every stellar nation in the galaxy. One young hopeful is Tadatos Lane, an orphan esper from Terra. The final stage of the academy's entrance exam is a perilous mission simulation aboard an actual derelict starship. The applicants depart for the ships in groups of ten, but when Tada's crew arrives on the Esperanza, they are horrified to discover that they now number eleven. As the test progresses, things go awry and the atmosphere grows increasingly tense. The crew members begin to suspect sabotage, and Tada appears to be the likely culprit.

Won the 21st Shogakukan Manga Award for Shoujo in 1975 (tied with Poe no Ichizoku).

* Includes a short story called Seireigari which was later republished as a bunko volume under the name. It includes the same stories featured in this manga.

A collection of very complicated adult sci-fi short stories with difficult concepts about time and destiny. (Source: Prisms)

As winter draws to a close, German boarding school student Thomas Werner dies one morning. He leaves behind a single letter addressed to his fellow student Juli that reads "Here is my love. Here is the sound of my heart."

With his faith shaken to the core by the words, the scholarly Juli sinks to the depths of despair. His cynical roommate Oscar finds himself watching over Juli's fragile mental state while keeping his own feelings for Juli under wraps. Then new student Eric enters the school - and he has an uncanny resemblance to the deceased Thomas...

As winter draws to a close, German boarding school student Thomas Werner dies one morning. He leaves behind a single letter addressed to his fellow student Juli that reads "Here is my love. Here is the sound of my heart."

With his faith shaken to the core by the words, the scholarly Juli sinks to the depths of despair. His cynical roommate Oscar finds himself watching over Juli's fragile mental state while keeping his own feelings for Juli under wraps. Then new student Eric enters the school - and he has an uncanny resemblance to the deceased Thomas...

The title takes place in 16th-century France and tells the story of the historical Queen Margaret. The Japanese title of the series is identical to the title of the 1845 novel by Alexandre Dumas.
(Source: ANN)

Description from Viz :
The story A, A' raises a troubling question : How would you feel if your lover died - and was replaced by a clone ? Could you recreate your relationship with someone who was physically exactly the same but didn't share any memories of your life together ? in 4/4, teenaged Mori flunks out of an ESP training program. But when he meets Trill, a beautiful Unicorn, his latent abilities begin to blossom...In X+Y, Hagio uses science fiction to explore questions of gender and sexual identity. Time has passed, and once again, Mori finds himself inexorably attracted to a member of the unicorn race - but this unicorn is male...and so is Mori.

X+Y won Seiun Award in manga category in 1985

A Cruel God Reigns portrays the tale of two step-brothers – Jeremy and Ian – as they strive to discover their separate paths towards redemption. Jeremy, a sensitive but outgoing 17-year-old, is delighted to hear the news of his neurotic and excitable mother's remarriage to a wealthy British man. However, much to his horror, his sweet-talking new step-father, Greg, soon begins to exhibit a disturbing trait: he is a sadistic pedophile and loses no time in making Jeremy his target. Months of horrific, systematic abuse drives Jeremy to desperation; and he sabotages his step-father's car with the hope of eliminating him. The resulting accident, however, kills his mother along with Greg. Winner of the first Osamu Tezuka Cultural Prize Award for Excellence (1997).

A high school senior without self-esteem thinks she's an iguana. Her mother claims that whenever she sees Rika, she sees an iguana instead of a real human. Because of this, Rika has never received or was shown any love by her mother. Rika's younger sister Mami has been getting all of the love and attention by the mother. (Source: M-U)