How a Realist Hero rebuilt the kingdom is a great anime, but I would say it has a little bit of fan service/adult content. First of all, the MC has a harem and there is a lot of ecchi. Female characters do wear revealing clothes and many are sexualized throughout the show. Lastly, there are references to adult content like sex and SA. However, compared to other modern isekai with a season 2, the fanservice is very low and it is overall wholesome.
