A second season for How a Realist Hero Rebuilt the Kingdom will premiere in January 2022.
How a Realist Hero Rebuilt the Kingdom is originally a novel series by the writer Dojyomaru, and published by Shosetsuka ni Naro, and later Pixiv. The novel began in 2015, and was followed by a light novel and manga adaptation in 2016 and 2017 respectively.
Kazuya Souma is an average contemporary youth who gets summoned to another world facing the threat of a Demon Lord. Having no real combat experience, he impresses the king with his modern knowledge of agriculture, infrastructure, and logistics.
— 「現実主義勇者の王国再建記」作品公式 (@genkoku_info) September 25, 2021
The king abdicates his throne and crowns Kazuya the new king. Faced with a growing threat and unburdened by lofty cultural hangups like nobility, Kazuya is direct and pragmatic in improving the kingdom to face the coming threats.
You can find a summary of the series (via J-Novel Club) below.
“O, Hero!” With that cliched line, Kazuya Souma found himself summoned to another world and his adventure–did not begin. After he presents his plan to strengthen the country economically and militarily, the king cedes the throne to him and Souma finds himself saddled with ruling the nation! What’s more, he’s betrothed to the king’s daughter now…?! In order to get the country back on its feet, Souma calls the wise, the talented, and the gifted to his side. Five people gather before the newly crowned Souma. Just what are the many talents and abilities they possess…?! What path will his outlook as a realist take Souma and the people of his country down? A revolutionary transferred-to-another-world administrative fantasy series starts here!