Read Girl and Science Manhua:
They were childhood friends, and she had always been more powerful than him. But when they accidentally travelled (summoned?) to another world, it was finally time for him to become the knight in shining armor! He had to find her first though, since they were separated... Come and witness his fight to be better in a crazy world where monsters roamed and technology was so advanced your amputated limbs be re more.. stored to perfection...