If you're looking for manga similar to Steins;Gate: Eigoukaiki no Pandora, you might like these titles.
Revolves around Kurisu Makise as she tries to save Okabe Rintarou from his uncontrolled leaps in time. Kurisu must decide if she will save him as his lover, or not bring him back to the main timeline with her morals as a scientist.
The manga follows Gekitetsu Amo, a 17-year-old protagonist who does not stand out in school, but under the excuse of "eliminating harmful elements from the world" begins committing mass murder.
Moriyama Rin was born with an incurable disease. I came to love the girl who spent her high school life hiding that fact. At our last cultural festival, we had our live concert and spent the last moments of the festival together—After that, Rin died. Then, I experienced a time leap...
The first story is a retelling of the story of Aladdin, with a couple of the names changed – but with a Hope/Crosby movie thrown in with a touch of Cinderella. The second story is yet another Ham Egg story, this time involving an abducted girl taken back to the ice age and a time machine that transports him into the future, when the human race is leaving to colonize Venus.
In approximately the year 3000, humankind arrived at the peak of its civilization, but is losing its will to keep living. It follows a girl, called "princess" by those around her, living on a small island with a fifty person colony and a shinning coral reef. She is descendent of Moon people, and it focuses upon how her ancestor supposedly came to Earth.
About a boy who was brought up by a robot, and was bullied for that in the future where Earth was conquered by aliens, and people are just living boring lives without any problems and ambitions.
When the Guyver, an alien life form, adopted the body of young Sho, it endowed him with super powers, and propelled him into an ongoing war with a secret organization. Now Sho and the girl of his dreams find refuge in a secluded cave, until renegade Hyper-Zoanoid Aptom appears to tell Sho the awful truth about his father's death. When Sho's trauma keeps him from transforming into the Guyver, Aptom performs some unlicensed therapy.