Hiraheishi wa Kako wo Yumemiru

Hiraheishi wa Kako wo Yumemiru (平兵士は過去を夢見る) is a light novel series written by Okano Yuu and illustrated by Kusugi Toku.

The novel series was adapted into a manga series by Suzuki Izo and published by AlphaPolis Web Manga.

Plot
It details the life of a mid-rank soldier who died at the very end of the war against the Demon Race. Fortunately for him, he wakes up to find that he's a baby again, in the embrace of his real mother, years in the past. Determined to avoid the chain of tragedies that took his beloved ones away from him, he takes advantage of the advancements in swordsmanship and magic that developed during the war (as we all know, wars are when many scientific breakthroughs tend to happen), and tries his best to prepare for the demon invasion as well as strengthen himself with maximum efficiency.