When Akira announces he was a boy in the first book "Ai wo Utau Yori Ore ni Oborero" so does the fact Akira goes to Dankaisan the boys school next to St. Nobora (Mizuki's school) Things start to get rough when pressure against Mizuki dating a boy from that school rise.
(Source: MU)

Mizuki is the female “prince” of her all-girls school and the lead guitarist in an all-girl rock band. Akira is the male “princess” of his all-boys school and wants to join her band. Love may be on his mind, but romance is difficult when everyone keeps mistaking Mizuki for a boy and Akira for a girl!
When the lead singer of Blaue Rosen announces she is moving overseas, Akira does all he can to convince Mizuki and her bandmates to let him join. But will a resistant Mizuki allow him into her band, much less her heart?
(Source: Viz)

[Taken from ShoujoMagic] :

A collection of Shinjo Mayu's earlier (and less smutty) short romance stories.

1) Bare the Heart (Kokoro wo Hadaka ni Shite). Mina is a high school freshman with a crush on her math teacher...who also happens to be her cousin Yukiya! Mina has always been very precious to Yukiya, and at times it seems like he can see straight through to her heart, but can he ever see her as a woman and not just his cute little cousin? How long can Mina's flirtations go unnoticed by Yukiya (or by the sadistic and lascivious chemistry teacher, for that matter)?

2) A Vampire at My Neck (Kubisuji ni Banpaia). Be careful when you go groping in the dark...you might just find a vampire! That's what happens to Hitomi. Now she's attracted to Kairi despite what he is. Or is it because of what he is? Kairi has a powerful charm...but is he too charming? Dangerously charming?

3) Hold Me, Melt Me (Dakishimete Tokashite) Ryou is a high school sprinter who's racing for a different kind of goal--his pretty track manager, Airi! He says he wants chocolate from her on Valentine's Day, but...is that a delicious metaphor for something sweeter? Whatever the case, it melts in the mouth!

4) Examine Me Gently (Yasashiku Mite ne). Sanae just had her appendix removed. But while she waits in post-op for her surgery wound to heal, she starts to develop another malady--love sickness! And her handsome new attending physician, Dr. Touya, is the cause! What can cure Sanae's ailment? ...A sponge bath, maybe?

Omake: If you have ever wondered why Shinjo Mayu's female characters have such big breasts and why her heroines seem so young...then you must read this omake! It is a great insight into the mind of Shinjo Mayu!

[From ShoujoMagic]:
Juuna's uncle gets her to enroll in the school where he's principal. The only problem is that it's an all boys school! With all those rabid guys around, Juuna needs someone to protect her. In comes Shibuki to be her bodyguard...but Juuna wants him to do more to her body than just guard it!

There's a rumor that high school freshman Aki is involved with Masaya, a candidate for student body president next term. Aki thinks of Masaya just as her best friend, but to make sure of the matter, Masaya's younger twin brother Naoya appears! Aki begins to be seduced by Naoya's forceful manner...

Then one day, Masaya collapses. When Aki goes to wish him well, she's relieved to see that he's okay. While she's there, though, Naoya asks her out on a date, and he's being much gentler with her than usual. Aki musters up her courage and tries to tell Naoya how she feels, but not only does Naoya do an about-face and command Aki to date Masaya instead, but another girl confesses love to Naoya right in front of her!? What's Aki going to do...??

-- ShoujoMagic

Aine never wanted to be a writer; she just created some erotic song lyrics for the sake of entering a contest. When she bumps into a man she doesn't know and looses the lyrics, she thinks she'll never see them again, but she thought wrong! He turns out to be Sakuya, a famous rock vocalist known for his sexy persona and lyrics. When he invites Aine to be his new lyricist, she finds herself quickly sucked into the harsh world of showbiz... and the even harsher world of falling in love with a guy that millions of girls love just as much!

Fianse Shitai Yukimi is a high school junior and cheerleader already scheduled for her first marriage interview. She's seen a disappointing picture of her nerdy potential groom -- and he has such a weird name -- so Yukimi has every intention of rejecting him, but she's still curious to go and see what a marriage interview is like. Later that day, Yukimi meets her ideal man at a football match and inadvertantly begins cheering only for him -- despite the fact that he's the opposing team's quarterback! He gives her a bold and seductive response. Ah, if only Yukimi's marriage interview could be with a guy like this... But why won't the sexy quarterback tell Yukimi his name...? (taken from shoujomagic)

1) Let's Make Love!! (Make Love Shiyo!!). (v01 ch1 to 6) Mari Nishimiya is a high school junior who's tired of playing it safe. Less concerned with her summer session and more with achieving the love of a lifetime, she ventures to a foreigners' pub with her childhood friend, Yuuta. There, she meets Leon Gardner, an American dancer with a talented tongue (...meaning, he's bilingual)! While Yuuta disapproves, having an unrequited love for Mari himself, he and other enemies of this international relationship may be powerless to stop it when Leon joins Mari's class as... (!!!)

Let's Make Love!! - Farside Story (Make Love Shiyo!! Chou - Bangaihen). (v01 omake). Shinjo Mayu parodies her own work by inserting new dialogue into some of her pages from v01. It's the tale of the Gardner family, where Leon is Papa, Chris is Mama, and Mari is their daughter! Additional curiosities included.

Let's Make More Love!! (Motto Make Love Shiyo!!). (v02 ch7). Mari wants to have an adult Christmas with Leon. Why is Leon so set against it?

Let's Always Make Love!! (Zutto Make Love Shiyo!!). (v02 ch8). Attending the international wedding of Leon's friend, Randy, has Mari thinking in a new way about her future. But when Mari begins to feel strangely sick and misses her period, the circumstance forces her to make an early decision! But Leon suddenly has to leave for America!? Why?? Mari isn't going to like the reason Randy gives her...

2) I Don't Need Any Scenario! (Shinario Nante Iranai!). (v02 ch9). This ground-breaking short story was Shinjo Mayu's first work to contain a provocative sex scene and to mark her as a pornographer! Read the freetalk to learn more! Yuuya is the manager of the drama club, and he's very strict and exacting about how the student thespians handle their roles. Chiharu is supposed to be playing a woman in love, but there's no emotion in her performance! So it's handsome Yuuya's job to teach her how to long for a man... Was this scenario in the script!?

3) I Want to Be Painted with Your Color (Anata no Iro ni Somaritai). (v02 ch10). This short story is Shinjo Mayu's debut work. Kazumi Inoue wants to be transformed by the magic of a white wedding dress, and then painted in a man's color. The biggest delinquent in school, Kazuya Sakurai, wasn't who she had in mind, though! He's intent on painting her a different color -- why? Kazumi will have her wish - a transformation through the magic of a wedding dress - but not in a way that anyone expects!

(v02 omake). A whopping nine pages covering a variety of topics. Get a sneak peek into Shinjo Mayu's office, find out her favorite stories and characters, see Leon with a top knot, see Leon touch Yuuta in inappropriate ways, and at long last the burning question is answered: How are chihuahuas significant to this serialization!?

One day while walking home from her job, Kurumi Akino finds a wounded young man, and saves his life. He mysteriously dissapears after that, and leaves only the name Hakuron?. Next thing she knows she's been kidnapped from her school, and is on a private jet with that man, heading to China. It turns out she saved the life of the most infamous mobster in Hong Kong, and he wants her to stay with him.

You can find A Tale of Happier Times (v06 extra) in the anthology Motto Oshiete.

WARNING: This series contains strong "consensual rape" situations, strong language, scenes of graphic sex, rape, violence, murder, suicide, glorifies the mafia and black market. It is recommended that you be the legal age of consent in your country to view this story.

Himeno's chest will hurt if any boy touches her because she has the diamond of the heart. However, when she was young, she befriended two boys -- the gentle Mamoru and the blunt Keigo -- who are able to touch her without harming her. Without knowing about the diamond of the heart, both Mamoru and Keigo promised to protect Himeno. When some people threaten to take Himeno's heart, who else will protect her but her knights?
(Source: MU)

Math teacher mamiya nagisa is teased by his horny students at an all boys high school on a daily basis. One day genius high school student, sakura minato, transfers from America. Minato jumps in to save nagisa who is teased by the students, but is told, "i want to sleep with you." When he asks senior teacher tsukioka for advice, he is attacked by him. What will become of nagisa's purity?

This series of stories started as just the oneshot Pure Love Strip, and then Doting Love Strip and Lavish Love Strip were released.

From ShoujoMagic:

Pure Love Strip
Yuuko is in her third year in Junior High (freshman in high school in US). She is a glasses wearing...four eyed nerd. She's suddenly getting tutoring from perfect Ryuunosuke-kun, but that is not the only thing that Yuuko is getting tutoring for...Yuuko's dangerous summer hoilday is about to begin!

Doting Love Strip
The continuing story after Pure Love Strip. After their first time.. he has started wanting it... every day!?

Lavish Love Strip
The continuing story after Pure Love Strip and Doting Love Strip. Perhaps the smuttiest installment so far? Yagami is tutoring Yuuko so that they can be in the same High School... But is his need for a wild sex life going to interfere with Yuuko's studies??

The summer of a seventeen-year-old girl. Since her female friends backed out at the last minute, Mai ends up going on a trip with 3 boys. What's more, it is her first time meeting them!! This... this might be...!?

Misaki has dreamed to be had by Michiru, so much that she would die for it. Knowing that he is a player, she goes to find/meet him at a bar. She gets had by Michiru. But after that, is it over? Or will he still remember her?
"The beautiful and most mysterious poison 'flower'...is tempting every part of me..." Misaki loved him from the bottom of her heart... because she loved him... and longed for him... but now Misaki is slowly losing hold of Michiru...!?

From ShoujoMagic:

This book is a collection of steamy stories!

Story 1) I Want to Be Bound by You
Ayuna comes to visit her brother at the hotel where he works, but a case of mistaken identity leads her into the royal suite and the arms of Takano, a handsome young businessman. He's Daidou Corporation's ruthless behind-the-scenes manipulator who handles all of its dirty work. Nothing gives him more pleasure than corrupting that which is pure, and... Ayuna is pure.

Story 2) Steal My Body Away/ Your Heart, Your Person
Terumi and Kazu have been sleeping together at hotels, but the relationship is entirely physical. Can it be called love? This is when Terumi suddenly meets Kyuuji, an intense young stranger who boldly uses her to escape a fight. Because she takes offense, Kyuuji then pursues the fight to appease her. He steals Terumi's heart away, but will the jilted Kazu allow Kyuuji to steal Terumi's body?

Story 3) The Devil's Mask
Natsuki is content in her relationship with Showa, a boy in her tennis club. That's why she despises herself for drinking too much at a party one night and sleeping with the student body president, Kazuomi. He's a devil and a genius who publicly wears an angel's mask, and he tells Natsuki that if she doesn't want her boyfriend to know about her drunken infidelity, then she'll continue sleeping with him in secret. The secret is in danger of being exposed, however, when Kazuomi joins the tennis club. No, not that secret -- Natsuki's OTHER secret.

Story 4) Painful Love
Everyone is a little afraid of Ryuuichirou. He's a gang leader who hangs out in an alley that Norika passes through each day to get to work. Norika is attracted to his dangerous aura and the gentility he displays towards her, but a painful past haunts him that has the potential to be both spiritually and physically painful to Norika.

A kind hearted guy who grows up eating apples and whose parents own an tartlet cafe, wants to be the ultimate gang leader. A villainous girl who was brought up in a family of gangsters wants to be the owner of a tartlet shop! How will the pair cross one another's path with their dreams on the opposite party?

Renjouji Kiriya holds the coveted position of the number 1 ranked host at a high-class host club "Chateau de l'Amour" in Tokyo. The Chateau de l'Amour specializes in providing the company of beautiful, cultured men to female customers. Few people know that the popular Kiriya is actually Yamada Kotarou, a boy from Nagasaki who came to Tokyo to find a way to repay his parent's debt.

Some of the other hosts, jealous of his position, are determined to get past his perfect facade to discredit him. Kiriya will have a hard time stopping them, especially after a former customer dumps an adorable 5-year-old girl on him, claiming he is the father. The only thing that could make this situation more difficult would be the arrival of his Nagasaki girlfriend Miharu, who knows nothing of his career as a host...

Miko is a shrine maiden who has never had much success at seeing or banishing spirits. Then she meets Kagura, a sexy demon who feeds off women’s feelings of passion and love. Kagura’s insatiable appetite has left many girls at school brokenhearted, so Miko casts a spell to seal his powers. Surprisingly the spell works—sort of—but now Kagura is after her!
(Source: Viz)