From ShoujoMagic:

Haru, an energetic, honest, and sweet young girl, meets the popular grade schooler Yashima at a bowling rally, and she unintentionally develops a strange interest in him. He's very forward about wanting to date Haru. However, Haru is in love with her childhood friend, Yuusaku, who thinks of Haru like family and rejected her love confession before he left for America one year ago. But now Yuusaku is back! How will both boys respond to learning that they have competition for the role of most important man in Haru's life?

First volume includes a yomikiri, Let's Go Youth Heaven.

From Easy Going Scans:

A gangster girl in high school decides it's time to live life properly after graduating by marrying a nice man and living a normal life. However, her past as a gangster constantly threatens to come out from time to time and she has trouble holding back. And when she has a daughter...apples don't fall far from the tree.

Smart, successful and good-looking Iwaya Sumire works for a big newspaper. However, her boss asks her to leave for being too "perfect" a woman. Feeling angry and dejected Iwaya returns home depressed, and most of all lonely. However, when she finds an unconscious young man lying in a box out the front of her home, she takes him in since he looks like a dog she used to own called Momo. She dubs him Momo and decides to "keep him as a pet." It's the start of an unexpected life together as they overcome obstacles and become quite attached to one another. But can love like this exist?

This manga won the 27th Kodansha Manga Award for shoujo in 2003 (shared with Hachimitsu to Clover).

Atori has an unusual part-time job... she’s a demon hunter! After school, she hunts demons for a mysterious organization named N.U.E. To kill her enemies, she unsheathes the saber hidden within her hair. However, Atori is actually half-demon, but she has forgotten her past. Despite this, she's been able to overcome many difficulties as well as befriend those from both species. Unfortunately, her once calm life is beginning to quake as a terrible shadow now looms over her...

Miku is on the same tennis team as her childhood crush, Tomo-nii.
Not only can this guy kick ass in tennis, he's also good-looking and super nice! The only thing that Miku doesn't like about him is his brother, Natsume. Completely opposite from his older brother, Natsume is known to play girls, and be a basic cocky pain in the neck.
But one day, Miku finds out something about him that ends up shocking her to no end...!!

Yoshimatsu Hotaka is the president of the manga club and is always diligent with his studies and club responsibilities, even though he has a habit of skipping class activities. Although he looks like a regular honor student in reality he is overwhelmed by melancholy and haunted by his past misfortunes. Meanwhile, he makes sure to admire and watch Awaya Nika, the beautiful, bright, radiant, super cheerful swimming club's female ace. He's content to continue his high-school days like this until the P.E. teacher makes him take a private swimming lesson to make up for all the other lessons he had missed; a development that would forever change the dynamic between him and Awaya. What's the cause of Hotaka's bitterness? What does he want to hide?
How does Awaya Nika have more in common with him than he could ever imagine?

Sequel to Memory of the Future (Mirai no Kioku) Kento is mild-mannered, straightforward and quite honestly, a bit boring. At 26 he's landed his first full-time position teaching at high school and does everything he can to make his grandparents, who took him in to raise after his parents' tragic death, proud of him. Unfortunately Kento is gay... and they ~don't~ approve. Enter Akira, a ticking-time bomb with a perpetual evil smirk, a ridiculously flamboyant wardrobe and a tendency to hit on anything that moves. Akira's everything Kento isn't... including drop-dead gorgeous and mindbendingly annoying. It's almost a miracle that the two of them have been dating for over a year!! But after all that time, Akira's still keeping some secrets... secrets that aren't going to reflect well on Kento's choice in a partner. Would Kento's grandparents ever survive the shock of their son dating the child of a sex-worker and an alien? Or will they, as Akira puts it, "cough up their pacemakers"?! Does Kento care more about his family's opinion of him, or his high-maitanance lover's deep-seated social inferiority complex? An extremely sweet (and funny) story of two people who couldn't be more different, or more perfect for each other. (from doki doki)

A collection of 6 short stories, each a dramatic love story.

1) Crevasse by Sakurai Machiko
Is it right to just look him from far away? To never talk to him? Is it that there's really no reason to....

2) Te wo Tsunaide ikou by Nekoyama Miyao
Mikiko plans to date Sasaken after the image of his "back was suddenly stamped" in her memory at the entrance ceremony. But how will they progress after a misunderstanding caused by her kouhai, Nari-chan?

3) Aishiteru yo hana by Minato Rin
In a cruel twist of fate, right before Christmas, Hana's husband Tanesaburo is killed when he is hit by a truck. This is the bittersweet story of the young widow's Christmas.

4) Towa no uta by Mitsuya Omi

5) Cinderella no kutsu wo sagashite by Niiya Moeri

6) 1999 nen chikyuu saigo no koi by Takahashi Rie

From MangaHelpers:
It's fairly obvious to Terui Chiaki that her classmate Ajikawa Yoshio has a crush on her. He is completely not boyfriend material in her eyes and, even if he was, Chiaki already has a boyfriend. Their mysterious teacher Mr. Yamada sees this relationship between the two students and offers an experiment. He is able to make copies of people and objects and does so with Chiaki, creating a copy of her, except the copy has no knowledge of her boyfriend. Yoshio will hit on the Chiaki copy, who is named Koaki, and he'll try to make her fall in love with him. After a specified amount of time, the copy and original will be combined back together and which ever love is stronger between the current boyfriend and Yoshio will overwrite all other emotions. So this love experiment begins and both Chiaki and Koaki, being the same person, thinks Yoshio has no chance in hell but with each passing day, some feelings begin to bubble.

From UTBCT:

"Their love was a dream."

A member of a boy band, a very popular and charismatic musician, the guitarist of Dada!! I've been dreaming of such yearning love with a boy, who is just out of reach everyone present. But I really would want to live this love that has become a reality?

A collection of hearthwarming and romantic stories by Anashin.

A very short story (3 pages long) about a boy who transform into a girl to become a hero, but she has to collect stamps to be a real hero.

Late one night when Jun was out on his bike, he came across a drunk, half-naked girl sprawled on the side of the road. She came to just enough to be uncomfortably affectionate, but Jun took her to his home to sleep it off with gentlemanly discretion. It turns out that she is Kawase Narumi, his author mother's new assistant. Unfortunately, she has no idea what she's doing in her new job, so Jun's going to have to coach her. He's also going to have to deal with her habit of getting drunk, mostly naked, and cuddly. Jun's life will never be the same! [From Baka-Updates]

From Shoujo Manga Maniac:

1) Love Lab
The chemistry club invented a special hormone potion. Each bottle cost 500 yen. Riko-chan's boyfriend, Yuuki-kun himself is extremely cold towards love. Riko-chan hopes to move their relationship one step ahead, but in the end...?

2) Merry Kiss

3) Perfect Doll

4) Twinkle Twinkle

5) Cupid's Arrow

Kyousuke wants to be a cop. Because of that, he always tries to do the right thing and help others out. Well, while saving a girl from some bullies, they end up liking each other. Not to soon after, she needs saving again, and he ends up with woman's panties over his head, giving him super strength (pumped with horniness.) Not your normal super hero.

High school is difficult for most kids. But for Kayano, a shy girl whose single mother seems to work all the time, it's even worse than usual. She's so afraid of drawing attention to herself that she can't tell the handsome Kamijo how much she loves him until one day she finally gets up the courage to write him a letter confessing her feelings.
When she goes to give him the letter all her plans go awry. She's given the letter to the wrong person! Accidentally, she's given her love letter to Takeru Edogawa who just so happens to be the school principal's son, head of the delinquents and the notorious "Prince of Attraction"! To Kayano, he seems like Satan himself. Not only is he devilishly handsome, but he seems to take the utmost pleasure in making her suffer. Things only get more interesting when Kayano's mother comes home one day and announces she's getting married again --- To principal Edogawa! What will Kayano do when she has to live with this devil 24/7? How will she cope with her literal "Hell on Earth"?

Yona Ryouma, a normal high school boy, saves a man from another world at the cost of his own life when a mysterious earthquake occurs. The man, Emillio, uses a potion which apparently saves Ryouma's life. However, he is also changed into a girl in the process.

Emillio is actually the prince of this alternate world and he declares Ryouma as his wife, presumably on the context of saving his life. But what about Ryouma's life as a high school boy in his own world? And will he come to accept being the prince's wife?

1) The Guy With An Ideal Face
Noriko wants just one thing: "The Man with a Perfect Face"! To her friends' complete and utter shock, Noriko finds Takurou-kun, a man who meets all her unrealistic expectations. They go on a date, they kiss, and have what could be considered a perfect time, but then Noriko sees the real face of Takurou...!?

2) I'm Gonna Get Jealous
A girl who sees no point in becoming jealous learns first-hand how it could happen.

3) Love Slave
Kanano isn't sure what to make of her relationship with her upperclassman Ooba Yoshiya. After she first confessed to him, she hounded him until he agreed to date her, but the relationship seems to be on his terms, and poor, obediant Kanano worries that her love is one-sided. Then, Kanano learns that Yoshiya has a past with a girl who has the same face as her...? Who does Yoshiya think of when he's out with Kanano? How come he touched his old girlfriend but won't touch Kanano...!?

4) I Wanna Get Lovey-Dovey
Shihomi has had a crush on Sakayori since the day of high school entrance exams, when she got lost and he helped her. He's got a good heart, but he's extremely rough around the edges, and that's what's making it so difficult for Shihomi to confess. It took her two months just to say "good morning" to him, and every time she does, he seems to be in an incredibly bad mood afterwards? What's the source of Sakayori's attitude problem?

5) Well Excuse Me For Being Trendy
Mayu already has a boyfriend, but she can't help admiring Shuusaku's dashing good looks, which are increasing his popularity by the minute. It doesn't matter if his personality is as one-dimensional as his expressionless face, because it's looks that count! By chance, Mayu happens to learn about Shuusaku's secret crush -- and his expression is so darn cute when he's confronted about it that Mayu feels compelled to help him win his love. But Mayu's a trend whore at heart, and falling for Shuusaku seems to be getting fashionable...!?

1) The Turquoise Morning
A well known photographer named Jed Knox acquires a one-sided love from his time in a foreign country. Because the target of his crush, Sahab, said he would never love another since his wife died, Jed would never tell of his feelings. Oh but how Jed wished Sahab would love him even a little bit and that he could have Sahab's soul in his hands. Although ifrits (genies, etc) are magical wish givers in story, what could happen if they were real?

2) It's Time for Goodbye
It is the morning after and the student finally notices that the lover's room is exceptionally sparse.

3) LOVE-ING
A guy tells his friend that he's gay and in love with him, but his friend is surprised and leaves.

4) Playboy!
He has had it. His lover won't make love to him and refuses to stop seeing other women.

5) The Eyes of the Rose are Bombs
The prince-like Hansumi has an effect on everyone around him, except Mitsuda.

6) Aah Boyfriend
Suzuki can't stop fantasizing about his friend.

7) Garden of Despair
Isuka is still trying to come to terms with his feelings for his friend.

8) The Eyes of the Rose are Blind
Continuation of chapter 5.

9) Garden of Desire
Continuation of chapter 7.

10) Bad Boy
Continuation of chapter 4.

11) Go Go Boyfriend
Continuation of chapter 6.

12) Postscript

From Shoujo Crusade:

Kurai Karen is a rich ojou-sama with many suitors. She's in love with her butler, Ishibashi Megumi. Long ago, the two of them made a promise to be together forever. Now that they've grown up, Megumi seems to have forgotten, but Karen hasn't. A forbidden love between master and servant, what will happen to them?!

Extra story Sweet Guardian:
Kasuga Yuuki had always been in love with Himuro Makoto. One day she decided to confess to him and ended up rejected. On the same day she fell asleep on a supplementary class and ended up staying late at school. To her happiness, she found out that Himuro-kun was also still at school, but somehow he had a gun?! Moreover he tried to kill their school Chairman and admitted he is a hitman?! And later she ended up going out with him!? Is this all a dream?!

From Day of the River:

Our crybaby protagonist Hirahara Tsukasa hasn't always been a crybaby. Due to the death of her older sister Chihiro, Tsukasa hasn't been able to dam up the flood of tears ever since - even about little things.

She is further disheartened after moving to Tokyo from Hiroshima, especially after a series of incidents cause her and her four classmates to miss the bus and be late for the entrance ceremony on the very first day of the school term. However, it is precisely this event that ends up drawing her closer to maturity and fueling her determination to stop her crybaby tendencies. And perhaps, she may even find an unexpected love on the way...