Luigi is a tall man with dry blonde haired with blue eyes. He is described by many as an incredibly handsome man.
Luigi is a kind, smart and talented man; and his wife would often describe him as a wonderful husband.
Luigi Claes is the son of former Duke Claes and the current head of the Claes Household. Luigi used to be a quite ladies man back in the day that the number of women that wanted to get married to him were as numerous as the stars, but he is now just a middle-aged man madly doting on his family.
After Katarina was engaged to Prince Geordo Stuart, Luigi sought out Keith Claes from his relatives who was said to have strong magic powers. He took Keith as his adopted son which created problem in their house, almost causing Millidiana to divorce him. After he was able to explain Keith's background through Katarina's encouragement, the misunderstandings between the couple have been lifted and his relationship with his wife became better.
In his youth, he was a very popular man who was the apple of the eye of many women in high society. Even people who do not often partake in social circles know of his name, as like a "prince from a fairy tale".
Luigi and Millidiana formally met at a party where he was introduced by Duke Adeth. Unbeknownst to Millidiana, Luigi fell in love with her at first sight during that party. He enthusiastically spent that party all night with Millidiana, and immediately asked for her hand soon after.
While Luigi was absolutely in love with his wife, Millidiana had doubts about their marriage as she did not know that his proposal was out of love, which he didn't realize was a sentiment of hers until later. Thanks to a series of incidents after the adoption of Keith into the household, the two realized that they were misunderstanding each other and their love for each other was renewed. They are finally able to feel like a married couple after years into their marriage.
Luigi is very soft and lenient when it comes to his daughter Katarina, and would often spoil her rotten because of how much he loves her. Regardless of what antics and hijinks she gets into, he would laugh it off and forgive her without a second thought. In Fortune Lover, this lenience from her father made Katarina grow arrogant and haughty to an extreme degree.
Luigi loves his adopted son, Keith and treats him as his own at the very moment he joined the family. He entrusts taking care of Katarina to his son.
As a far of relative of the Claes, Luigi is acquainted with Viscount Coleman and is aware of the terrible treatment that he is giving his son Keith. As Luigi conveniently needed a new heir for the Claes household, he took Keith from Viscount Coleman, which he did not even mind as he did not consider Keith as his own.
- Luigi is very similar to Prince Geordo.
- Both men are described as fairy tale princes by the women in high society. They are both seen as very handsome and charming, and was considered the most sought-after man by their peers.
- Both men are in love with a Duke's daughter who does not believe that they are loved by them (both Millidiana and Katarina thinking that their fiancés are engaged to them because of duty or obligation). Their love for their female partners would lead to those partners being stared and glared in envy.
- In the StoryMe game, it is revealed that there is a lake in the Claes Manor the Luigi considers to be his favorite spot, where only his beloved people can come.
- When Keith in the game asks how many women he has brought to the lake, Luigi replies that only his kids and his wife has come to the lake. It is also the very same place where he had formally proposed to Millidiana before their marriage, as proof that she is the only woman he will ever truly love. 
- Light Novel Volume 5, Chapter 7
- My Next Life as a Villainess! StoryMe game, Episode 1 Keith Diamond Option