Leslie is a young boy with freckles and short hair which was neatly combed around his head. He wore standard orphanage uniform and the code "71584" implemented on his neck.
Not much known about Leslie's personality. However, Leslie appeared as a compassionate and cordial young boy, bearing a shy but friendly attitude towards Isabella. Leslie was also shown to be easily frightened, as he gasped at Isabella's sudden appearance.
Leslie was born in 2014, and then sent to Plant 3 a year later in 2015, growing up along side Isabella and several other children.
During his years, when he was unbeknownst of his fate of getting eaten by the demons, Leslie befriended Isabella and had been close friends. During a period of time in the orphanage, Leslie composed a tune which he then shared to Isabella after her insisting on singing the tune to her. Leslie's fate later remains unknown, but was assumed dead since Isabella described that he was no longer around.
Since the two are raised in the same orphanage, Leslie and Isabella had been close —if not intimate— friends during their childhood. Leslie was shown to be rather shy but kind-witted towards his friend, as she was the only person Leslie was willing to chant his tune to. Leslie, on a certain degree, seems to bear feelings towards Isabella, as he was shown to blush when Isabella insisted him on sharing his tune to her.