From Viz:
Miaka Yuuki is an ordinary junior-high student who is suddenly whisked away into the world of a book, "The Universe of th Four Gods". There she becomes the priestess of the god Suzaku, and is charged with finding all seven of her Celestial-Warrior protectors.

Story about friendship and truth, with of course, a supernatural box.
Begins in a middle school where a mysterious box appears before some boys

The series tells the full story of the Priestess of Byakko.

Yuu Watase Masterpiece Collection Volume 4
Story 1: Suna no Tiara - On their way to Eden, princess Tiara and her subjects are attacked, and only the princess survives. Follow her in her quest for revenge.
Story 2: Hatsuki Triangle: Hodaka Hatsuki takes on the personality and abilities of her old boyfriend everytime she touches a practice sword for the Kendo club. Kunie Kenshi is determined to make her normal once again.
Story 3: 700 Nichi no Blue - Oikawa Masumi tells about her work on a painting titled "Blue Magician" and the man who helped her.

Summary from Watase's Sorai:

Basically a really cute short story about being happy with the life you have.

Rejected by way too many good-looking (and unattainable) guys, Riiko Izawa goes online and signs up for a free trial of a mysterious Nightly Lover "figure." The very next day a cute naked guy is delivered to her door, and he wants to be her boyfriend!
Has Riiko died and gone to heaven? The cute guy turns out to be sweet, smart, a great cook, and lots more. And, better yet, he looks like a million bucks, which is what he's going to cost Riiko if she doesn't return him in time! Will she? Or will Night be taken back to the company and made into scrap metal?

A fun guide that teaches the basics of the art of manga by one of the most well-known mangakas in the business! Follow Eri on her journey to "become a pro and inspire people with dreams!"

Higuchi Asuka's mother dies shortly after she tells her teenage daughter who her father is. Only knowing the family name “Sudou”, Asuka goes in search to find her absent father. On her journey, she finds a guy being rather rough with a younger girl. Unable to resist, Asuka steps in by battering the guy with her motorcycle. When she discovers it was a big misunderstanding (Manato was just trying getting his sister Kazusa to go home), she drives them back to their house.
Once there, Asuka finds out that Manato and Kazusa are the Sudou family she's been looking for, but the father isn't there, not to mention their mother also being dead since long ago. With no other leads, Asuka decides to move in as Neesan (the big sister) until their father shows up. Things get tricky when love builds within the complex family relationship....

Zoku Shishunki Miman Okotowari (Sequel)

Yuu Watase's Masterpiece Collection Volume 5 consists of four stories.

1) Mint de Kiss Me -
There is a legend that if you kiss the man you like with a mint candy in your mouth, you can become one with your love. Misono is a rather superstitious girl who decides to test this out on Tohno-sensei, a young teacher she has a crush on. Unfortunately for her, she makes a mistake in the attempt to surprise him and instead kisses her fellow classmate Shindou. Of course this would be the time for the legend to work quite literally as Misono’s spirit enters Shindou’s body.

2) Genseika -
Chiya goes to school with her friends and witnesses one of them die suddenly as a flower bursts out of him. The three friends had been together since elementary school, the death hitting Chiya and Yutaka hard. When other people begin dying from the flowers, they investigate possible reasons for such usual deaths. To her surprise, she finds answers close to home.

3) Furimuke Romance! -
The hero of girls targeted by guys peeking into the locker room, Taka has quite the violent tomboy reputation. But all she wants is for some handsome guy to ask her out. A cheerful street vender, Ryouta gives her a special ring with a heart locket pendent to hold pictures. When two photos are enclosed, romance is in the air.

4) Hang in there Nakago (Part I) -
Involves the scenario where Fushigi Yuugi was actually done by real actors. Unfortunately, Nakago (stage name) is a lot more unconfident than the character he plays. At least his one main fan, an unnamed woman with flowers, is there to support him through his worries.

Collection of short stories:
1. Shishunki Miman Okotowari Ending - At long last, Yuu Watase brings us the final chapter of the Shinshunki Miman Okotowari series. Manato returns from America, but he doesn't come with the best news for Asuka. This might be the last time he returns to Japan.

2. Couple - Inaho has fallen in love with Takumi, the lead guitarist of a high school band. With hand-made gifts and her strange personality, she gets Takumi to ask her out. But only with a special biwa (a Japanese lute) can their relationship last.

3. Chikyu no Arukikata - Ayuki just got dumped. On the same day, she hurt her ankle during track practice. Later, Ayuki gets trapped on the wrong train to the coast. On this train, she meets Hiroto, a guy who has quit school in search of himself. Ayuki wonders if she should do the same.

[From ShoujoMagic]:

A special short story that was published in a freebie book put out in Sho-Comi, then added as an extra in the last volume of Zettai Kareshi.

Chima Nagatsu, a high school sophomore, has always been able to see spirits that have died but haven't passed on yet. She also has the power to banish them. One day she gets a job from her uncle asking her to banish the spirits in an all boys school. She reluctantly accepts only to find that one of the spirits, Tsukasa, is a boy whom she admires!

Tanpopo Yamazaki is a girl with a dream of attending a high school in Tokyo. Yet when her dream comes true and the famous Meio High accepts her, all isn't what it seems. Students are sorted only by family connections and wealth, meaning friends are nowhere to be found. Taking matters into her own hands, she starts a gardening club. As the year progresses Tanpopo gains what she's wanted (maybe even more) and one by one, people weave into her life in a way that'll change her life forever...

Takiko Okuda is a strong-willed girl living in the Taisho Era. She needs to be strong -- Oosugi, the one man she's ever loved, is a married man; her mother is terminally ill; and her father, Einosuke, has not been home in over a year. When at last Einosuke returns, it's with a notebook full of Chinese scribblings that seem more important to him than the death of his wife. Furious, Takiko steals away his completed translation -- "The Universe of the Four Gods" -- with the intention of tearing it to shreds, but the instant she opens it, she's surrounded by light... And it is said that this is how the legend of the Priestess of Genbu began.
(Source: ShoujoMagic)Included one-shot:
Volume 6: Ayashi no Ceres Gaiden

Kabuki Takitsugu is a son from a family of the "Fragrance Way", who has the special ability to smell out human scents. A girl named Hatsune appears before Kabuki while he is making money on school grounds by matchmaking people. But for some reason he can't smell Hatsune's scent.

Aya and her twin brother Aki thought they were going to a celebration of their sixteenth birthday at their grandfather's home, but the funeral-like atmosphere tips them off that something's not right. Their "birthday present" turns out to be a mummified hand--the power of which forces an awakening within Aya, and painful wounds all over Aki's body! Grandfather Mikage announces that Aki will be heir to the Mikage fortune, and Aya must die! But Aya has allies in the athletic cook and martial artist Y?hi, and the attractive, mysterious T?ya. But can even two handsome and resourceful guys save Aya when it's her own power that's out of control?

Volume 2 of the YuuTopia Collection.
1. Musubiya Nanako
Nanako has her mother's ability to see the red strings that bind to people together in love. At her parents match making shrine, Nanako is forced to bring couples together by binding their strings. But who is she to be bound to?
2. Perfect Lovers
Mitsuharu and Kana get into a car accident just after breaking up. They wake up just to find themselves in a dimension where homosexuality is normal and heterosexual relationships are illegal.
3. Memoir Girl
Katakura Hitomi does not like her new step-mother taking up all the attention of her father. In an abandoned school building, she meets a high school boy who becomes her confidant.
4. Hang in There Nakago (Part II)
Continues the tale from Mint de Kiss Me. (Source: MangaUpdates)

Itsuki Ringo (yes, her name means 'apple') is the top student of her freshman class with one talent: studying. Coerced by her mother into tutoring the abrasive upperclassman, Tsurugi Budou (who happens to be the brother of her crush, Tsurugi Minori), Ringo unwittingly finds herself butting heads with the rebellious Budou more often than getting any actual tutoring done. In an attempt to find out why Budou hates studying so much and skips tutoring, Ringo spies on him. She discovers a whole other facet to Budou's harsh character, and soon finds herself falling for him.

After being kicked out of her apartment, YuMi must find a place to stay, or she will be forced to return to her home in the sticks! Can she convince YoungHo to to defy conventional boundaries and allow her to stay at his place, at least until she finishes college?