>>279735994A bunch of teenagers got isekai'd in a fantasy world and lost most of their memories. They were somewhat forced to join the mercenaries - oh sorry, auxiliary troops - and to kill monster in order to survive - with a caveat. Some spells can only protect up to 8 peoples (I think), so after the leader types picked the best of the newcomers, they ended up with a bunch of rejects, MC's party, that struggled with killing a single goblin.
That's basically the introduction.