He is undeniably elegant and awfully cold. The player first meets Louis in the Palace garden where, prior to becoming the Princess Elect, you are searching for a legendary magical flower that can grant any wish. Louis mocks you for believing the legend and tells you to leave before causing any more trouble. 

He tends to keep his thoughts to himself and bears a tsundere nature, meaning he is initially cold and distant but gradually reveals a much warmer side of himself.

In truth, Louis' cold demeanour is due to his distaste for the upper-class lifestyle that was thrust upon him. He rebuffs the player initially but is secretly impressed by how you bear up under the pressures of being the Princess Elect. Louis greatly admires the strength and earnestness of the player, which he states is one of the reasons he falls for you.

As he was not born a nobleman, he often harbours the desire to leave his position as duke and wonders how the player, having also been born a commoner, can deal with the responsibilities of being Princess Elect without wanting to go back to being just a commoner.

This, however, is only a defensive façade that he uses to protect himself and fit in with the other aristocrats. Once he realises that he has someone whom he cares for, Louis is very protective and loving, the complete opposite of how he was initially.

Once he is more trusting of someone, he immediately becomes more gentle in his manner, in both the words he speaks and the way he says them. When around people he’s comfortable, Louis will sometimes smile, will be more inclined to humour and teasing others. He has shown himself to be quite supportive and friendly to those he favours, like when he’s assisted the MC with her situations in several other suitors’ routes, despite him having to accept the position of Prince Consort even when he hasn’t wanted to.

When he’s with the MC, Louis has a much more playful, softer side of him that comes out to play quickly. He’ll often tease to no end with her, but he’s also exceptionally sweet and honest, such as with things like the MC’s body and personality.

While he’s usually passive with others and, when the MC and Louis are friends, is quite uninterested in most things around him, when he’s with the MC, he becomes somewhat possessive and almost child-like in his manner. He can become aggressive quite quickly, especially when the MC is criticised or Sid’s around, and more so when the latter says something to provoke him.

(Bottom Line: tsundere)