Tengujin is a story about two twin brothers who live in a world where Eastern and Western Japan and splitting apart and have formed two warring countries. In this "idiot adult's world", many social issues press on society and drove it to war. Gods of the world, mainly tengu, influence the start and end of the events that lead to war such as Japan splitting into two, so the younger twin, Mozuku, desires to end the idiotic war the adults started and meets with the God of the West (Sai) with his older brother, Shinonome.
Zanouka, the second story in Tengujin, is about the former incarnations of Mozuku and Shinonome. Mozuku is a young bard who is the inheriting son of a feudal lord of a dead mountain with only poor people remaining on it. He keeps a rigid, realistic perspective on life and refuses to believe in things like tengu. While cleaning the tengu's small shrine, his beautiful voice attracts the attention of the tengu of the mountain, Tondonbou (Shinonome's former incarnation), who hides half of his face behind a mask. After meeting the tengu, Mozuku sets to seeking him out again, wanting to see what was hidden behind that mask.
(Aku Tenshi)

Compilation of short stories.
1) The Day I Become a Butterfly
There is a rumor going around school that Mikami can “hear” when one’s death is near. Uka has just turned fifteen, but doesn’t know how much longer he’ll live… Will the budding love between Mikami and Uka have a happy ending?

2) You At the End (Hate Ni Aru Kimi)
A short story about a guy sick of this world and the silent, unlikely boy who anchors him to it.

3) The Lonely War
Can men and women have platonic friendships? Suzu is determined to try.

4) Blue Cat's Tunnel
A story about one girl's hope to find a way out of her life...

5) Tokyo Alien Yulala
A young student's trouble understanding his classmate makes him think the boy may be an alien.

6) Planet Yours
An abused boy has trouble relying on his friends.

Note: stories 1, 2, 5 & 6 are shounen-ai, stories 3 & 4 are shoujo.

From CoyoMoose:

Due to her uncle's debt, Mozu is forced to marry someone she hates. So before she has to marry him she runs away to see the world before she is locked away forever. While on her journey she sees a man who goes flying through the air, and then disappears. Left amazed she travels in to town and is pulled in to a mountain guide shop. To her surprise, the man she saw flying through the air is now her guide. To HIS surprise, she is the spitting image of his former lover, Suzume.

Nagaru, an ordinary college student, suddenly confesses to his classmate Fugimoto. How will things turn out?

This is a short but sweet oneshot.

The flower in Itadori will bloom in the summer, taking his life as it took his sister's but giving others longer lives, but how can he leave his childhood friend Rakka behind...?

A sweet story about friendship and young love.

A short story about schoolboys love....This kind of makes you feel alive.

Adults--they just don't get the pressures of being babies! Thoughts on growing up from the Kindergarten of Evil students.

Futaba, whose father is an oceanographer, has transferred schools 8 times because of his work. Afraid of eventually being forgotten, she tries not to make any new friends at her new school.

[Summary By: Love_Blossom]

Akino can only see the man of the deep blue tree only when autumn comes. Over the years, her love for him grew deeply. Ahh if only he were human...

A short oneshot about someone who is taken in from the cold by the only person to notice him, a young man named Taiyou.
(from Psycho Pandas)

Pinky promise. If you lie then you have to swallow a thousand needles and your finger will be chopped off. Kiriko is a little girl who makes pinky promises with various people who expect her to pay for them, looking forward the day they run out of fingers to make promises with or break their promise. An adorable yet creepy 8 page oneshot.
(Source: Psycho Pandas)

From Psycho Pandas:
A short 16-page oneshot about the relationship between two high school boys who want to be together and the girl who won't let them.

From Storm in Heaven:

Chidori absolutely hates men. For her entire life, she's been forced to put up with a bunch of irresponsible, useless slackers, and she's sick of it. Can one innocent little lie change how she feels about men?

From DMP:
Nakagawa and Yokota are two boys very much in love with each other. Yokota is more open with his feelings, but Nakagawa is easily embarrassed of public displays of affection. Though they may be outwardly different, their feelings for each other are the same...their connection is such that they liken themselves to Dousaibou Seibutsu (Same-Cell Organisms).

Contains the Stories:
1. Same Cell Organism
2. I Love You
3. Lullaby in My Hand
4. The Letter in the Attic (Yare Ura Yuubin Monogatari)
5. To Make Angel (Tenshi wo Tsukuru) (Prequel)
6. To Make Angel (Tenshi wo Tsukuru) (Sequel)
7. We Selfish Two

A heartrending and heartwarming story about two twins: one who hates everything like himself and one who wishes to keep his promise from long ago.
(Source: Psycho Pandas)

Yoshinatsu is a one-shot about a friend that will not be forgotten.
(Source: sumomoyumeka.livejournal.com)

[From Storm in Heaven]:

This volume contains four of Yumeka Sumomo's short stories.

1) Natsukashi Machi no Rozione : a young woman struggles to realize the value of her childhood.

2) Icchoume Kikyouya no Hime-sama.

3) Boku no Shalala: about witch Shalala and a human boy

4) Robot: Sci-fi romance.