Manga with themes like politics, action (specially with levels or other ways that evolves them over time), kingdom building and other situations where you feel like the main character's power is growing. They can get vassals...
Fantasy and isekai stories featuring child protagonists. Some are actually former adults who were reincarnated or somehow transformed into children.
This list include manga with an at least partly European medieval/pre industrial inspired setting where fantasy elements such as magic, superhuman abilities and/or mythological creatures are prominent. Generally exluding: series...