Starting today I am a castellan

A story based on comic https://www.mangaupdates.com/series/nl6uadg/starting-from-today-i-ll-work-as-a-city-lord The story follows young merchant, who got the ability to travel between earth and certain fantasy world. He used that ability to start a new life in fantasy world and became a merchant. One day he meets a man who very cheaply sells him rights to small town...it was suspicious, but he accepted the offer. However the was a problem... it turned out to be ruined village with small castle! However, it had a little surprise, as previous owner told him to check out castle's dungeon.