When a forgetful man forgets everything, will he lose everything in the end?

About a young girl, a mummy man and an amusement park.

"Wh-Who are you?"

One day, the college student Taichi is spoken to by a stranger in a place that is very dear to him. He is informed by the man, who calls himself Zama, that the place may be gone. It is where the orphaned Taichi first met his beloved guardian Kanda.

Who is this Zama, who suddenly appears before Taichi? Taichi is anxious...

It is the near future and the age of criminal organizations fighting for territory with their own crew has ended as they figured that it was neither economical nor practical. The new method of territory warfare is done with each criminal organization hiring an assassin and betting their land on which assassin survives the modern day coliseum.

Bando Eiji aka Gun Mania is a top rated assassin for the Kuroyanagi group. A young man named Kusano Nonomura of the now overthrown Kusano organization seems to have a vengeance against Bando, the Kuroyanagi family and the entire criminal world. Blood will be shed very soon.

From Jshoujo Scans: Yorika Senoo is taking a picture of Yousuke Shiiba, the guy she likes playing soccer on her phone. She is then hit by the ball giving her the chance to finally talk to him. She returns home to have her dreams crushed as her father is being transferred to London. Not wanting to leave the chance to know Shiiba behind she decides to stay in Japan. Her worried parents allow her as she makes her way to her new share-house with a girl named Yuki Yoshihara...but when she arrives turns out Yuki is a guy not a girl, and his name is Yutaka Yoshihara. She got the kanji confused.

From MangaHelpers:

In 2019, childhood friends Yashio Kaito and Senomiya Akiho are in their last year of high school. Together, they are the only students in the robotics club, which has lost its school funding. Akiho is passionate about robots, and longs to complete building the robot her older sister Misaki began in this same club. Kaito doesn't really care about robots, and is obsessed with video games, specifically "Kill Ballad Online." However, he stays in the robotics club due to his friendship with Akiho. Now, just after Kaito is accused of cheating in his favorite game, Akiho decides to risk her club's existence in exchange for the funding to finally finish her sister's giant robot... [tethysdust]

From Damn Feels!:

Chidori only eats soy sauce ice cream from the Purple Valley shop because “It tastes the best!” she claims; no other place has the same flavor. While she’s there one day she encounters the person who made Purple Valley’s ice cream special. To her surprise, he has changed in a way that no longer resembles the boy from her memories…

A long time ago, a pair of twins were born. Back then, however, multiple births were considered unlucky, so one of the twins, a girl, was... crushed to death with a millstone, buried under the shade of a large mulberry tree. The girl's soul, lacking a fully grown spirit, could not reincarnate, and as such was forced to wander the world. Only after collecting 108 individual sources of human misery/worldly desire could she move onto the next world.

From Acme:

The story of a quiet, sensitive high-school guy who enjoys painting, and his complicated feelings.

Love, trust and friendship are very important values but also very fragile. In the lives of Maggie, Annie, Edison and Nick they unknowingly become tools for pain. Denying love, creating lies and keeping secrets lead to unwanted results and to a battle between two girls that either may never win. (by Aria)

From StarryHeaven:

Megumi Yoshida (nicknamed: Useless Yoshi **Yoshi-dame**) entered university prep school after high school but it was difficult to make friends. Useless Yoshida wanted to make friends and because she knew her classmate likes presents, thought that was the best way to make friends. However, she doesn’t have much money, and when asked for some cosmetics, she shoplifts. Afterwards, useless Yoshida joined the shoplifting group and though she felt guilty in the beginning, she soon became accustomed to shoplifting without remorse. However after reflecting on the hurt she was causing to the people who knew about the shoplifting, she stops shoplifting and decides to make everything right again by paying back what she stole. But standing in her way are the members of the shoplifting group, Yumacchi and her friends.

From Bakeneko's Lair:

Poor, poor Akatsuki Homare. He's gotten himself into a mess of trouble. Considering his arrogance, he's getting exactly what he deserves. Yes, Homare, life is a game of give and take. You don't only get to be on the taking side...

A woman thinks about someone from her past.

From Tokyopop:

A chilling dramatic series about Shinjyurou Mamiya, an embalmer in a nation where men of his profession are viewed as outcasts engaging in an unaccepted and unclean practice. For Shinjyurou, it's just a job. But in doing it, he's gained an understanding of death, and more important, what it truly means to live...

Yuusuke's senior, Ichijou, tells him an old horror story of an ill-fated lover who, rumor has it, was left to die in what is now the present-day basement of one of the school's buildings. Sent on an errand inbetween classes, Yusuke can't help but recall the story as he makes his way through the eerie surroundings, when suddenly...he blacks out... Released in volume 1 of the Finder series, Target in the Viewfinder.

Kyouya, top leading Japanese dancer, has caught the eye of Kunitachi, a company president. Kunitachi is arrogant and aggressive. He openly and publicly kisses Kyouya whenever he feels like it without Kyouya’s consent. Despite his possessive and aggressive advances towards Kyouya, he is seen in the the tabloids having a private meeting with a beautiful woman. Can Kyouya continue to play hard-to-get especially when this scandal has angered him to the point of confronting Kunitachi?

Oku meets Nana again after they slept together long ago. In the past, Nana was The Prince of Good Fortune. There was a jinx that any woman who slept with him would become lucky and their wish granted. So, Oku asks Nana to try sleep with him to see if he can also make guys lucky as well. However, Oku's purpose wasn't about luck but his secret feelings.

From The Queen 2 Hearts:

Once upon a time when gods' world is so close to the Earth. There are four god families symbolize East - West - South - North called Seiryuu, Byakko, Suzaku and Genbu. Kira is original god of Kouryuu - the central god family which is the most powerful. Someday, while travelling with his brother, Kira met with an accident which made him lose power and felt to the Earth. Later, while looking for the way to return Heaven, Kira met Shana and Senju. Shana is a boy who has a half of his body immortal, whose sister is kidnapped and he is on the way hunting his enemy. Senju is a female disciple of Sara - a predictor who has a half blood of god. After Sara was kidnapped by Seiryuu King, all of three persons also find the way come to Heaven so that save her and wipe out their enemies.

Nareh and Tareh are fraternal twins, Nareh the elder sister and Tareh the younger brother. When Nareh learns that Tareh has been accepted into the all-boys Ordinary School, she is shocked, and prepared to stop him at all costs...

From StarryHeaven:
In 2999, all people of the world had forgotten the existence of God. A seventeen year old girl in high school, Kisaki Aragaki, has been close to the Church’s Sister as a mother. One day Kisaki saw the Church being dismantled by workers and she encountered an Oni (Japanese demon) out of a worker’s body. Her father, Kenzo confessed that Kisaki is a reincarnation of her ancestress who fought against Oni with a Japanese saber called Katana of Oni. Then Kisaki took the inheritance of Katana of Oni and faced down the Oni.