If you're looking for manga similar to Knights of Ramune & 40 Fire, you might like these titles.
Ayako and 40 classmates are suddenly blown to the other world by the power of the girl. There, they are have to fight against the zombies.... Ayako goes to various war-related departments, such as assault soldiers and sanitary soldiers, to go to war and to go back to the former world - - !!
A boy goes looking for the legendary magicians who can save his village from a giant fungus, but he finds more than he bargained for.
Kain is a story about a blue-eyed boy wandering the countryside. He happens to be in a town controlled by "kidoushi." These kidoushi are people from the newborn country of Ren, who have a machine in their body, giving them power equal to an army in return for pain proportionate to that power. The power of the kidoushi is determined by the amount of gigai (the machine) taken up in their body.