Nurarihyon no Mago: Sennen Makyou, Kimetsu no Yaiba Recommendations
Both are shounen with a dark atmosphere at times (Nurarihyon is more light-hearted in the first season).
Both contain historical elements from Japan, although Nurarihyon's setting is modern Japan (for the second season, there is an important flash-back in Edo era rather than Taishou era for Kimetsu no Yaiba).
Both MC are fighting demons (youkai or ayakashi) who eat humans, but the MC is one quarter youkai himself (still far from Nezuko).
Both MC use a special katana to fight.
Both are Nekketsu shounen and both MC fight overpowered enemies (in season 2 mostly for Nurarihyon).
Both get stronger by training in a forest (season 2).
Both main antagonists are immortal