Kimetsu no Yaiba, Enen no Shouboutai Recommendations
Both shows are high intensity battle/action Shonen anime.
Both begin with tragedies to our main character's family.
Both shows have demons and demonic/evil themes and characters.
Both are dark battle fantasy anime with many intense battles, memorable characters and great art styles.
Both Anime have:
-Protagonist who have lost family in supernatural ways
-Protagonist join forces that attack said supernatural being
-Protagonist has a goal to find cause of supernatural phenomena
Both have high quality animation especially with fast motion scenes.