The Cloud Meteorologist: Storming the War-Torn Realms

Kumono Souta, a 40-year-old meteorologist, dies in a traffic accident and awakens as Tenki—a newborn in a fantasy world where skills have levels and magic exists.

Retaining all his scientific knowledge about atmospheric phenomena, Tenki discovers he possesses rare Cloud Magic. Combined with rigorous swordsmanship training under Marcus, a retired Level 7 adventurer, he begins forging a unique fighting style that merges blade and weather manipulation.

But this world is dangerous. War rages in the eastern territories. Monsters grow bolder near the borders. And Tenki's unusual reincarnation comes with mysterious system announcements that no one else experiences.

As he trains toward his 10th birthday appraisal, Tenki must master both sword and storm—because in a world where strength is survival, being "good for his age" won't be enough.

I am also posting this story on Royal Road under the username waya_27.