Tsukumo, Mutsumi

A classic yuri manga about a woman who leaves her husband for an old friend from school. There are two stories in this manga--one (Moonlight Flowers) is the main story, and the other (Midnight Flowers) is about the protagonist's friend's past.
Note: this manga contains rape.
(Source: Lililicious)

Also includes another unrelated story.

Moonlight Flowers

月下美人

Yamaji, Ebine

Ichiko Izumiya is a young student of English who would like to walk in the footsteps of her father is a translator of trendy American novels. She finally decides to confess to him that she is in love with Eriko, a law student. Ichiko will attempt to live out her homosexuality in peace and will be brought to wonder about the nature of her relationship: is she really homosexual or simply in love with a sensitive being who happens to be of the same sex? (Source: MU)

Love My Life

ラブ　マイ　ライフ

Amamiya, Sae

Plica-chan is the bittersweet, realistic story of Plica, a young lesbian looking for love in modern Japan.

The manga, which is written in 4-panel strip style, originally ran in Anise magazine, and now runs in the LOUD News, the newsletter for the LOUD organization. It can also be found online. Plica's comments are often on the nature of sexuality, the relationships between men and women, and between women and women.

The whole strip starts on a low note, as Plica returns from an ex-lover's wedding. But not too long into it, Plica meets Mari, for whom she starts to have feelings pretty soon.

(Source: okazu.blogspot.com)

Plica-chan

プリカちゃん

Takashima, Rica

The adventures of college student Rica, as she attends university in Tokyo and visits the gay and lesbian district looking for friendship and love. Rica's story is sweet and funny, realistic and a little wacky with a refreshing lack of self-hatred and doubt, but with no lack of real emotions.

(Source: MU)

Rica tte Kanji!?

Tokyo Love: Rica'tte Kanji!?

リカって感じ!?

Shiina, Ayumi

Takasaki Tomoka is a young girl seeking love. She had finally found her prince and slowly began to think of a way to speak to him. Tomoka met up with her childhood classmate from piano lessons, Miyazawa Arata and was invited to a performance by his band. There, she met the prince she had been admiring for many days. After becoming drunk, Tomoka confessed her love to her prince but problems arise with Tomoka having to take her love down through a dangerous path. (Source: M-U)

Anata to Scandal

You & Scandal

(あなたとスキャンダル

Takemoto, Izumi

It's the year 2269, and April Enus is working as a spy for the Alliance. She's known as "Venus" because of her special power: fatalities don't seem to happen when she's around. But is this power a blessing or a curse?

(Source: Lililicious)

Transistor Venus

トランジスタにヴィーナス

Wako

WAKO's "Presents on Christmas Eve" (or, as Syk and I prefer to call it, "All I Want For Christmas is Surprise Lesbian Sex"), is about learning to overcome the pain of the past and live in the present. Or, as we prefer to describe it: "You raped me? How could you do that, that's so awful!" "But I'm a woman." "Oh, OK, then. Lesbian rape is great. Can I have your name now?" "No. Less talk, more sex!"

(Source: Lililicious)

Seiya no Okurimono

聖夜の贈り物

Otosaki, Tsubaki

Itou, Chika

A collection of short stories:

Endless Narcissus by Otosaki Tsubaki
The protagonist wants someone who will love her and her alone, so she gets a clone of herself.

Hidden Meaning by Itou Chika
A writer and an editor are lovers. The writer keeps basing characters on her lover, and the editor wants her to stop because she's afraid that people at work will find out about their relationship.

Maintenance by Itou Chika
A woman fantasizes about the mechanic who works next door to her office building. These fantasies involve being the car the mechanic is fixing.

She, Her, Her, Hers by Otosaki Tsubaki
Sakuya is shaken up by her parents' divorce and is worried that her relationship won't last forever either. Her lover, whose parents are also divorced, understands her feelings and tries to reassure her.

Note: these are only some of the titles contained in this anthology.  In total, there are twelve stories.

(Source: Lililicious)

Girls Only

Loneliness... They meet on a park bench one night. They were just classmates, barely knew each other. Secrets... Something make them talk to each other, reveal truths about themselves. Warmth... In the chill night kisses and caresses are more than just lust, as they explore and discover. Love...? 

(Source: Baka-Updates)

Dame Ningen Jan

Matsufuji, Junko

"Our Fake Relationship" is the story of a relationship between a college professor and one of her students. Miyuki strikes a bargain with the beautiful Professor Aikawa: in exchange for sexual favors, Professor Aikawa will allow Miyuki to write a thesis that will give her enough credits to graduate with her class. Though their relationship begins on a sleazy note, this story contains a fair amount of sweetness as well.

(Source: Lililicious)

Our Fake Relationship

In Eve no Onna-tachi, by Matsufuji Junko, Aiko is unhappy in her marriage—her husband only married her to get ahead at work, and he's hardly ever home. Luckily, she has Kyouko, a woman she met online one lonely night. But when Aiko's husband suspects she's having an affair, their vision of a happy Christmas Eve together is looking less and less likely.

(Source: Lililicious)

Manga Like The Red Love Letter