From Midnight Scans:

1) Simple Kiss by WATANABE Ayu
Once in a while, we kiss in secret. We are not lovers. We’re just “friends who kiss”. This was supposed to be a simple relationship, but…

2) Guruguru Pon-chan Okawari by IKEZAWA Satomi
With a miraculous invention, a small dog (male chihuahua) turns into a human! This is the interesting story of Sakura (human female) and a chihuahua living together!

3) Akarui Mirai by MIYOSHI Maki
To Sensei, I’m just a “student”, but to me, he’s a “man”. Although it’s not a love that is permitted, will this feeling of love that I have for Sensei ever reach him?

4) Goodbye, Friend by KUMAOKA Fuyu
Kyoko was confessed to by the guy her best friend likes. Although her friend is very important to her, and she definitely doesn’t want to lose her friendship with her, she can’t bring herself to break up with him…

5) Kimi ni Tsugu Ishiko
July 7th. I dye my hair and turn into my dead twin brother. Both my twin brother and I loved the same girl, and I can’t tell her the feelings I have for her because it is the punishment I gave myself…

From MegKF:

Because of her fathers job, Aki was raised in England. So when she moved back to Japan she was teased horribly for being "foreign". Now Aki is also a very beautiful young woman, which makes it even harder to make friends and be accepted. After the coolest boy at school starts taking an interest in her, things only get worse. As jealous girls start to harass her, Aki shows a side of herself that even she didn't know about.

Yaya’s high school friends haven’t been very nice. They call her “Yaya the cry-ya! Yaya the misfi-ya!” But no matter how badly they act, Yaya is just too naïve and trusting to believe the worst of her friends. Hard-rocking, butt-kicking Nana is just the girl to grab hold of Yaya’s timid demeanor and turn it upside down. Nana exposes Yaya’s “friends” as slime bags, doles out punishment, and does it all with style. Can there be anything that terminally shy Yaya and hyper-confident Nana have in common? Well, for one thing, they’re the same person. -- Manga Updates

From Del Rey:

Yaya is a naïve and trusting girl. Hard-rocking, butt-kicking Nana is just the girl to grab hold of Yaya’s timid demeanor and turn it upside down. Can there be anything that terminally shy Yaya and hyper-confident Nana have in common? Well, for one thing, they’re the same person.

From Del Rey:
Ponta is a Labrador retriever puppy, the Koizumi family's pet. She's full of energy and usually up to some kind of mischief. But when Grandpa Koizumi, an amateur inventor, creates the Guru Guru Bone, Ponta's curiosity causes trouble. She nibbles the bone - and turns into a human girl! Now Ponta lives two lives: one canine and one human!

Winner of the Kodansha Manga Award for Shoujo 2000.