The Saga of Tanya the Evil, Vol. 12 (Manga)

Biographical Note:
After gaining a reputation as an excellent instructor from her exercises with the Northern Sea Fleet, Tanya gets saddled with the task of managing a huge batch of newbies on the Rhine lines alongside the 203rd. These green soldiers, lacking in both training and experience, need to be pruned down somehow--and what better place to do that than the most hellish battlefield this world has ever seen...?

Publisher Marketing:
When a great assassin is reborn in another world, he finds himself the heir to a long line of killers from the shadows. With both his modern-day knowledge and experience and the special magic and techniques of this new world, he could very well become the most unstoppable assassin in history...!