SUTERARE KISHI NO GYAKUTENKI!: MEGAMI TO HAJIMETA DAINI NO JINSEI WA DENSETSU KYUU NO EIYUU DATTA KEN

Alfred, a middle-aged knight of the Royal Guard who served the kingdom for many years despite being of commoner origin, is falsely accused of embezzling the Royal Guard's budget, stripped of all his possessions, and exiled from the country. Devastated by this sudden turn of events, Alfred is saved by the "Goddess of the Forsaken," enshrined in a shrine he has cared for for many years. Rejuvenated into a teenage boy by the goddess's power, Alfred's life is completely transformed as he becomes the master of legendary weapons and dragons. He then sets out to build his ideal nation, gathering together other "abandoned ones" like himself! (Source: Hifumi Shobo, translated) — Description from AniList community (anilist.co).