Since the beginning of time ninjas have been regarded as people with great skill and power, the Blazing NinjaMan (Shinobi Mantaro) is one such young man. There is only one problem, the era of the ninja has come and gone. How can Shinobi consider himself a ninja in modern day Japan (1990s) and survive the daily rigors of high school life.

From MangaHelpers:
Yasaka Tokiwa lives in an unusual time, and according to his dreams, it's about to become even stranger. He's been having a dream of a woman called Ri'in ever since the robot, who he calls Makina, came to his home. He and Makina attend the same school, where their other classmates include a secret ninja (Kusanagi Kanata) and a sorcerer (Yata Haruka).
When Tokiwa, the robot, the ninja, and the sorcerer rush to rescue the student council president from a demon, the boys find that they've all been having the same dream! What is going to happen to their world?

Who do you think lives next door? A college student?
A secretary? A foodie? A quiet sort?
Or a killer?

Humanity's peaceful days all at once transform into an unspeakably odious hell.
The sudden invasion of wasp-like insects, along with gargantuan "dolls" wielding their enormous alien weapons, annihilating everyone in their path.
In the middle of the chaos, high school first-year, Iruma Ikaruga, fights to save his best friend and his beloved senpai from the dolls' assault with an unyielding spirit.
However, all that awaits him is despair.
Just what are the enormous puppets known as "Dolly"after?
What fate awaits Iruma?
The curtain has risen on humanity's "puppet show" of unimaginable despair, and the battle for survival has begun.

From Kodansha:

Class troublemaker Ryu Yamada is already having a bad day when he stumbles down a staircase along with star student Urara Shiraishi. When he wakes up, he realizes they have switched bodies—and that Ryu has the power to trade places with anyone just by kissing them! After figuring out the workings behind this new and amazing ability, Ryu and Urara take full advantage of the situation to improve their lives. But with such an oddly amazing power, just how long will Ryu and Urara be able to keep their secret under wraps?

One social outcast unleashes a cross counter that will change the world! A raging storm of fighting action!

Shotaro Mitarai has given up on life, but when he visits the great forests of Mt. Fuji to end it all, he's attacked by the Suicide Hunters. On the tip of a gruesome lynching and faced with a tragic death, the seeds of rage sprout within Shotaro! What course of action will he take from within the inferno of anger?!

Awaken! Stand and fight! Let the gong of your soul sound true!

The spin-off of the popular fantasy manga "Fairy Tail". Consists of 3 volumes

Volume 1: Kengami no Souryuu / Twin Dragons of Sabertooth
Sting, who became the master of Sabertooth, Rogue, Yukino, and Minerva together perform jobs together, but...? What is the danger approaching their guild and the whole continent!? The episode that was not shown in the original story is now being told!!

Volume 2: Rhodonite / Road Knight
Spin-off of Fairy Tail following Gajeel and his past.

Volume 3: Raigo Issen / Flash of Great Lightning
The story centers Laxus Dreyar, the Thunder God Tribe, and the time they were affiliated with Blue Pegasus.

A story about a long-necked girl's love life:
Kanoi Natsuki and her childhood friend Itsuki visit the same school and there seems to be more between them besides friendship. As a Rokurokubi, her quirk of stretching her neck is normal for her and her surroundings, but it's not always her choice to stretch it and although she has feelings for Itsuki, she can't tell him what she feels. Ultimately, she has to go through misunderstandings and shame.
Itsuki, meanwhile, manages to make any awkward situations dissolve or maybe not?

From Manga Box:
One day, a yakuza gang member is attacked in Roppongi, Tokyo. This is only a prologue to one man's revenge story, triggered by the events of twenty-two years ago. The flames of revenge burn in the darkness of the city. By the author of Hitoshi Tadano, Chief of Special Operations, Kimio Yanagizawa.

Tegami Bachi (or Letter Bees) are couriers that deliver important letters and packages throughout the land of eternal dusk, Amber Ground.

The story revolves around Lag Seeing, a young boy who was born on The Day of Flicker, 12 years ago when the man-made sun went down for unknown reasons. The manga follows his ambition to become a Letter Bee and how he follows the path of his idol Gauche Suede who suddenly went missing one day...

N/A

Misaki Hayato returns to his hometown and enrolls in the same high school as his two childhood friends. A lot has changed in the years he has been gone, his former best friends are seemingly distant from each other and leading relatively normal high school lives. Hayato's sudden arrival soon changes that and sends shockwaves through the entire town's delinquent population with his willingness to do anything for his friends and his love for a good fight.

Plants have taken over the planet.
In 2017, the vegetation in Tokyo rose up and toppled human society in moments.
The few survivors are forced to live in the relative safety of a subway network, but supplies are running low.
Join an average high school student named Akira as he challenges the plants in a struggle for survival!

"Three years ago, he had the same posture.
Three years ago, he had stood behind Miyuki.
Yes.... Compared to three years ago, it had changed."

Set three years prior to the present time, Tsuioku Hen tells the events that would change Miyuki's world drastically, as well as the events that led Tatsuya to become what he is now.

(Adaption of Light Novel v08)

A girl who can see the future. Another girl who knows if what you're telling is true or not.

Jang sung-gi who is always misunderstood as a pervert and a worthless man. He meets a mentor who suddenly turns him into a very charismatic man? A tale of how an average guy who turns into the greatest "pick up artist" and a story about misbehaved men who are constantly trying to pick up girls.

From Easy Going Scans:

Lin Xiaoyou, childhood friend of Xi Yu, died at the age of 14, but her spirit refused to pass onto the afterlife. Instead, she stuck around and became Yu's "guardian angel" due to a promise she made to him. Under Xiaoyou's constant guarding, Yu hasn't had a single girlfriend even though he's already 24. Being in a proper relationship has become his goal in life, but such a simple wish brings about a series of terrifying incidents. Is Xiaoyou really a "guardian angel", or is she actually an "evil spirit"?!

Hyun-Su Jung (29) was scammed by Jung-Mi Kim and is now in debt of 900,000$. He is being chased by loan sharks and ended up kidnapping Jung-Mi Kim's daughter, Ha-Yeon Lee (17). But when Hyun-Su Jung calls to demand ransom, Jung-Mi Kim tells him she doesn't care about what happens to her daughter and hangs up. What will happen to the kidnapper and his victim?

From: Easy Going Scans

DoAh Lee, a seemingly "normal" high-school boy, gets caught in a strange and embarrassing situation. Before he knows it, he is blackmailed into becoming the manager for a team of quirky, unruly, not to mention slightly lazy, heroes. Will he ever go back to his "normal" high-school days?

From Hokutonogun.com and HappyScans:

A former professor of archaeology, Hieda Reijiro was expelled from the Japanese Archaeological Association for claiming that youkai exist. Ancient horrors come to life before our eyes as the youkai hunter wanders the land to find proof for his theory.

The included one-shot, "The Living City", won the seventh Tezuka Award in 1974.