If you're looking for manga similar to Alderamin on the Sky (Light Novel), you might like these titles.
The Republic of San Magnolia has long been under attack from the neighboring Giadian Empire's army of unmanned drones known as the Legion. After years of painstaking research, the Republic finally developed autonomous drones of their own, turning the one-sided struggle into a war without casualties-or at least, that's what the government claims. In truth, there is no such thing as a bloodless war. Beyond the fortified walls protecting the eighty-five Republic territories lies the "nonexistent" Eighty-Sixth Sector. The young men and women of this forsaken land are branded the Eighty-Six and, stripped of their humanity, pilot the "unmanned" weapons into battle...
In the future, warfare has been revolutionized by the invention of mechanical weapons called “Objects.” These Objects are overwhelmingly powerful, rendering traditional weapons like guns, tanks and fighter jets completely useless. Qwenthur is an un-athletic, but smart soldier who aims to work as an Object mechanic. Stationed at an Alaskan Object base, he meets Milinda, a stoic but beautiful Elite Soldier who pilots her own Object. As they learn to support each other in battle, Qwenthur begins to uncover the grim secret behind the Heavy Objects
Not wanting to remain a NEET, 30-year-old Arata decided to join a private military and security company. While having fun during the training and getting good scores, soon he has to face a real war.
On a continent ruled by chaos, the Lords have the power of a holy seal that can calm the chaos and protect the people. However, before anyone realizes it, the rulers cast aside their creed of purifying the chaos, and instead start to fight each other for each others' holy seals to gain dominion over one another. Shiruuka, an isolated mage who scorns the Lords for abandoning their creed, and a wandering knight named Theo, who is on a journey to train to one day liberate his hometown, make an everlasting oath to work together to reform this continent dominated by wars and chaos.