On May 9th, 1999, Raku Ichijou was born into the Yakuza heir. On June 7th, 1999, Chitoge Kirisaki was born into the Bee Hive Gangsters. Even though Raku may be the next heir to a Yakuza group, he's actually a normal highschool student who wishes for peace and quiet. However, when he meets violent transfer student Chitoge Kirisaki, his life takes a sharp turn for the worse!

What do you spend the time left of your life when it's measured in heartbeats? This is the story of Hato Iijima and Hatsu Takagi, connected to each other by a rare disease called "Tempocardy".

The main character (the blonde ponytailed guy - yeah, guy) is Aramiya Satoshi, who main ability is shapeshifting into any animal ...though at a few points he has plants growing out of him, so my guess is he can shapeshift into any living thing (including an elephant and a lion) I'm not sure if he was naturally born that way or if he was a biological experiment. Anyway, he's a pretty easygoing guy who just wants to be left alone to enjoy his solitary life in the middle of a junkyard, but apparently some army or another is always after him because of his ability, though he is able to fight off entire tank battalions before breakfast. (Source: Mangahelpers)

Crossover between Ore Monogatari!! and Nisekoi.

A story that takes place on the day Aira turned 14, and learned the devastating truth about the island she lives on, which is completely surrounded by a huge wall...

A boy who loves shoujo manga cannot find a girl who is willing to become his girlfriend. But he seems to have a strange and ill luck with a girl after over 50 confessions.

A special collaboration oneshot between Nisekoi and Haikyu!!

A boy and a girl are forced to join hands for all eternity!? In a land ravaged by an epidemic known as "Troy", the only people with healing arts capable of stopping the seizures caused by the disease are the Sisters. Although they have a high resistance to the disease, they are searching for a person who is truly immune, if they exist, so that they can find a cure. The main character is Sister Elraine, one of the Sisters who becomes infected with Troy. But, when she touches Kiri, a seemingly ordinary boy, her seizures stop. Could he be the one!? From Wikipedia: Due to its low weekly ratings in the magazine, Double Arts was truncated and ended at chapter 23 during early September 2008, in the 41st issue of Weekly Sh?nen Jump.

Updating

From the mangaka of Double Arts: William is a young boy who idolizes Aradoff, a character from a popular novel which told Aradoff's adventures, and always dreams of having a grand adventure on his own. William's meeting with the novel author finally puts him on an adventure to prove that the novel is not merely a fiction.

In the year 3333, everyone wears personants, technologically advanced masks, to maintain equality and peace, because they eliminate the "differences" in people that lead to discrimination and conflict. It has been 100 years since the government implemented this "personant system," so society has adapted. Yet one man exists as the only one in the world without a personant: the wanted criminal Damore!

A collection of one-shots publlished between 2007-2008 published on various magazines and the Nisekoi pilot chapter:1. Island (2007, Akamaru Jump)For the last 400 years, an island has been completely surrounded by walls, isolated from the rest of the world. Aira and Marue have always dreamed of voyaging outside the walls, where lies a devastating truth unbeknownst to them.2. Koi no Kami-sama (2007, Weekly Shonen Jump)Tsuchibe Taichi, a boy who loves shoujo manga and believes in love above all else, ironically has the worst luck in love. His latest attempt in love is at the new transfer student, but a strange otherworldly force seems to be repelling him from her.3. Williams (2007, Weekly Shonen Jump)William is a young boy who idolizes Aradoff, a character from a popular novel which told Aradoff's adventures, and always dreams of having a grand adventure on his own. William's meeting with the novel author finally puts him on an adventure to prove that the novel is not merely a fiction.4. Personant (2008, Jump SQ)In the year 3333, everyone wears personants, technologically advanced masks, to maintain equality and peace, because they eliminate the "differences" in people that lead to discrimination and conflict. It has been 100 years since the government implemented this "personant system," so society has adapted. Yet one man exists as the only one in the world without a personant: the wanted criminal Damore!5. Apple (2008, Young Magazine)The main character (the blond ponytailed guy - yeah, guy) is Aramiya Satoshi, whose main ability is shape-shifting into any animal... though at some point he has plants growing out of him, so he is able shape-shift into any living thing. I'm not sure if he was naturally born that way or if he was a biological experiment. Anyway, he's a pretty easy-going guy who just wants to be left alone to enjoy his solitary life in the middle of a junkyard, but apparently some army or another is always after him because of his ability. Luckily, he is able to fight off entire tank battalions before breakfast.