Super Dragon Ball Heroes: Dark Demon Realm Mission! is a spin-off manga.
It tells the story of the conflict between the Time Patrol and the Dark Empire.

A seinen take on Saito's classic Survival. It tells about the drama of those who survived the fall of a meteorite on the Pacific Ocean after a failed attempt of destroying it with a missile. Cities are destroyed by big earthquakes, food runs short, illness spread quickly. In the midst of this scenario, Ootomo, the main character of this series, will do whatever in order to survive.

what happens when gamers are summoned back to the real world in their game avatars

Its been 15 years after the last Great War. While the scars of wars appear to have vanished on the outside.In truth, the world has become a much harsher place.Follow the journey of Felix and Bay on their quest to find someone from their past.

In the Steins;Gate - Hiyoku Renri no Sweets Honey series:

V.1 - Hiyoku Renri no Sweets Honey

V.2 - Motto Hiyoku Renri no Sweets Honey

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• Hiyoku Renri no Sweets Honey Final

Newly-transferred girl, Oribe, falls in love with the most popular and charismatic boy of the school, Sagara. But, Oribe is not what she seems? The tale of the mecha girl with the heart of a maiden unfolds!

Ex-licenced by Dark Horse Comics.

A decaying, old satellite is headed straight for Tokyo, and the city is three citizens shy of total evacuation. Hard-boiled detective Watanabe remains in the abandoned gotham, searching for a gaunt, desperate Machida, who is wanted for attempted murder; and Chiaki, a stubborn housewife who doesn't believe the burning rubble will hit Tokyo, also remains behind. But Chiaki is wrong. And when the satellite does hit, the three find the city is less abandoned than before. Someone was riding that satellite down from orbit, and that someone wasn't born on earth!

Trigger Keeper (トリガーキーパー, Torigā kīpā) is a two-part one-shot created by Daisuke Ashihara. It is the first precursor to the World Trigger manga series.
(from the World Trigger wiki)

17 year-old Qi was diagnosed with an incurable disease at a young age. Doctors warned that she would probably die by the age of 20; however, Qi's genius with robotics allowed her to create robots to act and hands and legs for her when her body became too weak. Yet despite all her genius with robotics, Qi's dream to replace her dying body with an entirely robotic one seems an impossible one. However, just as Qi's body seems finally ready to give out and she is on the verge of death, something unexpected occurs...

Never far from the future. In this world, all children are gathered up onto an island known as the "Juvenile Circle". They receive their education there until the age of 18, when they graduate and go into society as adults. A boy named "Shizu" was overcome with strange feelings of anxiety the day after his graduation. Were they directed towards becoming an adult? Does he want to remain a child? It was neither of these. Anxiety embraced Shizu. The anxiety would lead him towards the "truth" of his world.

It centers on a girl named Wakaba Himekawa, who is aware that she is growing up slower than other people, but otherwise lives a peaceful life. On the same day that she finally gets her first period, her childhood friend Takaya confesses that he loves her. While Wakaba had never felt that way for her friend before, she is still happy, if confused. As she is about to answer Takaya's confession, an alarm suddenly sounds, and a broadcast begins that will change her everyday life.

The series stars Azuma and Metabee as their friendship is put to the test when a meteorite collides into their town.

After the end, a young girl and her overprotective giant robot father figure travel the world salvaging supplies and avoiding the threats of the wasteland.
A roadtrip-style story about these two characters, the eager scavenger and her clumsy- but loving- mecha pal.

From MangaHelpers: Luca's friend Will, who is from a lower-class segment of society, has gone missing. Luca's only clue to find his friend is his fondness for a certain club in the entertainment district, where a woman named Yue performs. Will had always said they should go there together sometime. When Luca goes down alone to try to speak to Yue, though, he ends up being beaten badly. Luckily, Yue herself finds him, and takes him to her friend Takaomi to be patched up. It soon becomes clear that Will has fallen victim to a chimera sickness that is becoming common in the lower classes. Luca is determined to find his friend, and to save him. [tethysdust]

After the end of the Vajra war in 2059 AD , a mysterious "Var Syndrome" suddenly appeared in various parts of the Galaxy, afflicting life forms, even gargantuan Unamushi (Eel bug) native to the planet Pipre. Result of research revealed that people who posses a special singing voice is expected to have the ability to calm the Var. Interplanetary Civilian Military Contractor: Xaos, chose the trio of female idol group "Thrones" - the candidate to start the demonstration test of the power of song: "Project Thrones". Valkyrie unit of the Xaos Pipre branch: "Echo squadron" will escort Thrones, and the novice pilot Kinjou Kaito will be ecstatic when escorting Pirika Polywanov. Kaito, knowing the sorrows and passion behind Pirika's unfriendliness, inspired him to "change" to the man who protects Pirika.

When a spacetime warp sends the Autobots and Decepticons to the Japan of another dimension, they get involved in Mazinger Z's fight against Dr. Hell and Baron Ashura.

Mazinger vs. Transformers is a cross-over manga featuring the characters from the Mazinger and Transformers franchises.

The six chapters will each be drawn by a different artist.

The final act of 7SEEDS. What became of the people who survived to the end?

Young men and women were cryogenically frozen as part of the “7SEEDS Project” in order to prevent the destruction of mankind. They came together and safely escaped from the collapsing underground. After taking on such daring struggles, they are determined to survive in this world, and they have now begun working to build a new “life” on the island of Sado.

It focuses on a boy named Yamano Koichi, who is one day revealed to be the heir to the supernatural powers of an alien named Babel, who was stranded on Earth 5000 years ago and built the biblical Tower of Babel. Koichi becomes Babel II, armed with supernatural powers and served the Three Servants: the shapeshifting Rodem, the giant, pterodactyl-like Ropross, and the humanoid aquatic robot Poseidon. With his newfound powers, Babel II seeks to put an end to the ambition to Yomi, a man from the Himalayas who seeks world domination.

The tenth manga series based off of Toaru Majutsu no Index. An original side story written by Kamachi Kazuma and illustrated by Kisaragi Nankyoku, it focuses on the past of the Level 5 Kakine Teitoku.