Don't worry about spoilers here. There is nothing to spoil.
This series is about an emotionless killer reborn in a fantasy world in a dinasty of emotionless killers.
Here is what I got to know during the first five episodes:
Lugh is the main character, reborn in the family Tuatha Dé.
Lugh is very clever. Lugh is very skillful. Lugh is worthy of the name of Tuatha Dé. Lugh is a very serious person. Lugh is incredibly powerful already as a child. Lugh has immense amount of mana. Lugh is an incredible mage. Lugh is a good cook. Lugh is a good fighter. Lugh is fantastic. Lugh i popular, because he is fantastic. Lugh helps. Lugh is attractive. Lugh is elegant. Lugh is courteous. Lugh is cheered by everyone. Lugh is even better than his father. Lugh is even better than anyone in his family. Lugh is even better than anyone among his predecessors. Lugh is still fantastic. Noone can be like Lugh. It's impossible to be nearly as good as Lugh. Lugh I am the happiest girl in the world for I am your servant. Lugh I wouldn't want to be a Tuatha Dé because then I could not be your servant. Being your servant is the goal of my life.
Meanwhile, Lugh's personality is: He is emotionsless. He is serious. He is goal-oriented.
Lugh's father is: He is emotionless. He is serious. He is goal-oriented. He is proud of his son.
Lugh's mother is: Silly.
Lugh's teacher: Wants to stay with Lugh forever after knowing him for a few days, because Lugh is simply fantastic.
Lugh's servant girl is: Happy to be Lugh's servant. Her goal is to be an even better servant of Lugh. Has big boobs.
Every moment, every scene, every monologue, every dialogue is an exposition about how incredible Lugh is. I don't know what kind of sick wanabe self-realization dream this is, but it is utterly boring, and after a while gets irritating.
By the way, the whole story has an eerie resemblance to Mushoku Tensei. Just without any sign of personalities.