A rumored girl seems that she can't graduate unless she takes extra classes and also pass the examination test with a 60. She thinks that there's nothing to do in the school, but while studying....she finds....

This is extra story can be also be found in the manga, Chocolate Christmas.

1) Mimitabu no Riyuu (A Reason for Earlobes)
Yamaguchi is a notorious womanizer. Some men admire him; others can't stand him. Ishikawa is definitely one of the latter. Nevertheless, when Yamaguchi's latest girlfriend dumps him, Ishikawa jokingly offers to comfort him with his own body. Unfortunately for Ishikawa, Yamaguchi takes the offer seriously. And, to make matters worse, Ishikawa discovers that he can't say no!

2) Yubisaki no Biyaku (Love Potion Fingertips)
Ishikawa and Yamaguchi are dating, but Yamaguchi's lovey-dovey behavior makes Ishikawa sick. Hoping to put Yamaguchi in his place, Ishikawa suggests that they "see other people." But things take a turn for the worse when each one catches the other with a beautiful woman.

3) Kuchibiru no Teppen (The Top of the Lip)
Ishikawa usually wears an irritable scowl. So why is he laughing and smiling so happily? Is it because he likes homemade sweets... or the cute girl who made them? Consumed with jealousy, Yamaguchi's patience is pushed to the limit.

4) Tsumuji no Mannaka (The Center of the Hair Whorl)
Ishikawa's nightmare is in danger of become reality. His boyfriend, Yamaguchi, is trying to win over his family! Fearing for his future, Ishikawa forbids Yamaguchi to visit his home, but Yamaguchi is determined to get close to the Ishikawas, one way or another. If Ishikawa won't accept him, then maybe Ishikawa's sister, Hitomi, will...

5) Ushirosugata no Natsu no Neko (The Summer Cat Turns Its Back)
After bad news from the doctor, a man reminices about a young man he went to school with, but then young man appears and he hasn't aged...

Extra) Te no Hira no Ue (On the Palm of Your Hand)

The son of a famous pianist, music student Shinichi Chiaki dreams of studying abroad and becoming a conductor like his mentor. Unfortunately, his fear of flying grounds his lofty plans! As he watches other classmates achieve what he has always wanted, Shinichi wonders if he should quit music altogether.
Then one day he meets fellow student Megumi Noda, also known as Nodame. This oddball girl cannot cook, clean, or even read a music score, but she can play the piano in incomparable Cantabile style. And she teaches Chiaki something that he has forgotten: to enjoy his music, no matter where he is.

Winner of the Kodansha Manga Award for Shoujo in 2004.

Keidai Saeki is a high school student who remembers his past life in Pompeii, living as the Italian warrior Sirix. His friends around him are all also reincarnated - although they don't quite remember things the way he does. Keidai's wife from the past? She's now a middle school boy - while his best male friend is now a cute girl?! Throw in a case of love at first sight, and you have a new look at romance - manga-style!

From HMR:
This is the sequel series to Sexy Simpleton, but don't worry you won't be lost! Eun Bi, the popular CF model, is back in modern times with her ancient Chinese boyfriend. Yet the adventure's not over yet, as she's transported back into ancient China. Will she manage to find the shoes that can bring her back?

From ADV: Imagine a Neon Genesis Evangelion where choosing the right girl is more important than saving the world! That's the gist of Angelic Days--the hit manga that Eva fans have been waiting for! Based on a popular PC and Playstation 2 game released only in Japan, Angelic Days takes the angst-ridden Eva pilots and sets them in a lighter, brighter world.

Sakuya used to be a fearsome high rank vampire until he fell inlove with Atsumi. Now, he's fallen so low that he can't even drink other people's blood because only Atsumi's blood suits his taste. The problem is, Atsumi is not only a guy, but also a vampire hunter... Their love is more than just complicated, it's a game of life and death for them both!

From Tokyopop:
Dabin Choi is the daughter of Seoul's most powerful crime boss, and daddy's little girl has the hots for Eugene, the son of one of her father's 'friends'.
There's just one problem: Eugene isn't into Dabin. In fact, he thinks of her more like a little sister. (The kiss of death!) To make matters worse, Dabin's new classmate is none other than the son of her father's long-time rival. Soon, everyone at school begins playing power games that would make their fathers proud!

Poor Yuzu is an orphan who's too clumsy to hold a job. She's reduced to living in a playground -- until a handsome stranger named Hassaku informs her that she's heir to a fortune, and whisks her into a world of wealth, power, and more hot suitors than she can shake a scepter at! But there's a catch: Hassaku must turn this klutz into a lady of refinement, or Yuzu will lose everything!

Also included in this manga is an extra story called Naughty Honey:
"The boyfriend I made in college cheated on me."

When she caught her boyfriend sleeping with another woman, Kayako Ueno broke his front teeth... and it will cost her a hundred-thousand yen to repair them. So she takes a part-time job as a home tutor-- for playboy Haru-kun.

[From Enchantment Scans]:

Natural Angel is a series of three oneshot stories in a sequel to the popular series Angel Lip.

Story 1 - "Natural Angel" : Natsu, a fashion model, struggles to find satisfaction in her line of work. Just as her self-esteem hits a new low, a mysterious lipstick called "Angel Lip" appears before her, boosting her confidence in herself as a model.

Story 2 - "Milky Angel" : When she was young, Sumire made a promise to a childhood friend to succeed as a model. Years later, haunted by her past experiences, she has long withdrawn from modeling. Then one day, an old friend comes back into her life. Can Naoki convince her to return to the world of modeling?

Story 3 - "17-Seventeen" :Moe thought her relationship with her popular schoolmate Gou was over for good. But things have a way of surprising you...

Oneshot from Sono Kuchibiru, Itadakimasu

Miku and Natsume have always been fighting with each other until Natsume suddenly asks Miku to pretend to be his girlfriend!!! At first, Miku is quite opposed to the idea, but slowly… This mismatched couple, of a super tall guy and a girl often mistaken for an elementary student, fall in love.

From Shoujo Crusade:

Kyouka, a sixteen-year-old, will be a winner today, the first day at the new school to which she has just transferred! She will definitely get a great boyfriend and say her goodbyes to those lonely days!! Kyouka has two brothers who love her a lot. Every guy who comes close to Kyouka is kicked out by them, thus she has no boyfriend. But she finally found an ideal prince... or that's what she thought. This guy, Maki, is actually a perverted prince!?

* Also includes two short stories in volume 2:

• Nanisama?! Oresama
Satomi loves Yuuya a little too much and is totally wrapped around his little finger. But, if this continues, instead of becoming his girlfriend, she'll forever remain his gofer. Will Satomi do something to find out exactly where she stands with Yuuya?

• Ijiwaru wa Kuchibiru
During Shiori's fifteenth spring, she fell in love with the idol Shuu Kitamura. She was even lucky enough to get to meet him in person, but she realizes he's nothing but a fraud! However, due to certain circumstances, Shiori becomes Shuu's personal assistant!?

Arisa is a former yankee [delinquent] who changes her ways to gain the attention of Ren, a studious boy. Her efforts finally pay off when Ren asks her out. She's supposed to be really happy now that she has him as a boyfriend, but for some reason she can't stop thinking about Issei, her next-door neighbor. What happens when Issei forces Arisa to be the lead vocalist for his band? Arisa has to decide: who does she really want to be with?

1-3) Blue Grey Dream
After the failure attempt of eloping with his customer, Shiki (Purple Ghost), a male prostitute, gave up his hope for love… until Ootori-sensei came along. Will Shiki finally find what he had been looking for…!? So what if there's a huge gap on their social standings, what's so wrong about living and loving for the moment? Enjoy this forbidden love story in the red-light district.

4) Untied Heartbeat
Shinobu and Washizaki parted ways in the most terrible of circumstances and after the many years that have passed, Shinobu is still scarred by the incident. When Washizaki returns to Japan and seeks treatment for cancer at Shinobu's hospital, Shinobu must face his past and find a resolution to the difficult feelings he's hidden deep inside.

5) Heartthrob Prince
Noriaki, a normal Japanese high school student befriends transfer student, Zeid, a prince from overseas. As Zeid accustoms himself to Japan, Noriaki, although frustrated with Zeid's broken Japanese, finds the prince increasingly more charismatic and charming. Can Zeid charm his way into Noriaki's heart, and ultimately, his bed?

1) I'm Not Your Steppin' Stone
Construction worker Sakai Kazuya is a 23-year-old man in love. Unfortunately, the object of his affection is the younger sister of Ezumi Masashi, an 18-year-old elite whose house he has been working on. In order to dissuade Kazuya, Masashi lies that his sister is only interested in high achieving men. Masashi offers to tutor Kazuya so he can pass his senior high school exams, but will Kazuya be able to afford his extortive price?

2) Tell Me You Love Me
Masashi's classmate Saitou tries to get between him and Kazuya because he deems Kazuya as being an obstacle to Masashi's success.

Extras) Break Time
Saitou starts dreaming during class.
A Day with the Stupid Couple I
A Day with the Stupid Couple II

3) Lovely
Kazuya insists on taking the exams despite the fact that he is no longer interested in Natsuko. He bans Masashi from seeing him till the exams are over but then Masashi sees Mogi Kousei pulling Kazuya's pants off?! (features Mogi Kousei from Kawaige)

4) Marshmallow Honeymoon
It is summer and Masashi wants to go on a holiday with Kazuya but the latter has work lined up so he can afford the new air-conditioner.

From Nakama:

Kaibara Yousuke is a third-year college student looking for employment. During his second year, he'd immediately rebuffed his classmate Nakayamada Kazuki's offer: “Won't you have sex with me?” But that time, Kazuki's declaration of, “I could make you feel so good, you wouldn't be able to think of anything else,” was the beginning of their relationship. At first, Yousuke would shy away from sex, but he was healed by the unexpectedly tolerant Kazuki, and was gradually captivated.

A small intense boy, Fei, suddenly appears in front of Masaki who just got dumped. But why does he lick her tears?

Jinny is a famous model with those gorgeous long black hair but little does everyone knows that she is in fact actually Ahjin, a high schooler who has short hair, wears glasses and only does modelling for the sake of her uncle! Ahjin has a crush on Dohoon, one of the coolest guy in school. But when Ahjin (dressed up as Jinny) found out that she'll be living in the same apartment as her crush, she's thrilled! But how can she keep her secret from Dohoon, whom he himself adores the model Jinny!?

Haruka is a owner of a dog; however, the dog is no ordinary dog. He is the wildest boy in her high school. What exactly is their relationship...?

The fate of the world rests on one man's shoulders. Or, to put it more exactly, it rests on his balls.
In a freak sealing accident the Queen of Terror is sealed into Satou Kohta's balls, thus preventing her from reigning destruction on the world. However, a lesser devil, the incompetent horned tsundere loli Elyse, has been sent up to Earth to release the Queen at all costs. The only way to do so is to make Kohta ejaculate, and Elyse only has 30 days to do it.
The battle for mankind has begun, in Kohta's pants.