Kujou Hikaru / The boy in the mansion

Kujou Hikaru (九条ヒカル) is the Dark King's life and in the epilogue he is introduced as Hikari's brother, but for most of the series he is not named so he is usually referred to "The boy in the mansion" (館の少年).

In the mansion
He is cared for by the Zakenna Butlers and is never allowed outside the mansion grounds. However, regardless of their restrictions, he manages to get away more than once. He is a fun loving young boy but his passion for pleasure soon wilts as he craves to know the world outside of the mansion.

Meeting Hikari for the first time
In episode 21 he first met Hikari, by walking and saw her, then after seeing her, a connection was made as then it was the Cures had to protect Hikari from Circulas while he was protected by the two Butler Zakennas. However, they were seeing each other even when the Cures began to fight, when he left, then Hikari woke up making her feel confused.

Relationships

 * Kujou Hikari - first met him in episode 21 and at first she seems somewhat afraid of the connection they share as two sides of the same coin: Darkness and Light. Hikaru himself is not evil and Hikari soon realizes this, giving her all to help and protect him. In the epilogue, he becomes her brother.
 * Baldez, Circulas, Uraganos, Viblis - They see themselves as the boy's guardians and Pretty Cure as a threat to him one day becoming the Dark King thinking that he could be destroyed. Baldez however has other plans and seeks to awaken the boy's power by letting him meet Kujou Hikari since Darkness and Light are just two sides of the same coin.
 * Zakenna (Butlers) - They are the boy's caretakers and something of a Nanny. The are always buying toys for him to play with and teaching him how to use them.

Trivia
He would later share the same name as Hoshina Hikaru from Star Twinkle Precure