Spencer Simmons (Japanese: スペンサー, Supensā) is Tuesday's brother.
Spencer is a quite tall man. He has bright yellow hair.
He is intelligent considering that he received a first-rate education from a young age. He was also expected to follow in his mother’s footsteps and become a politician in the future.
Spencer called his mother to come and read Tuesday's message about leaving home and living on her own. Checking at her IC card history, he figured she is in Alba City. He also noticed that Tuesday's guitar is missing and figured why she may have run. His mother then left, telling him to deal with the situation as she was busy.
Catching the train, Spencer headed to Alba City. Arriving in the city and knowing the rough location of Tuesday, Spencer went searching for her. He met Carole Stanley landlord in front of her building. He asked him if he had seen Tuesday and explained who he was and her situation, but the landlord denied seeing her. As he kept searching, he went into the Mars Lounge, where he was Tuesday singing, but decided to leave without saying anything.
When Valerie got Tuesday back and locked her in her room, Spencer visited her, telling her that he enjoyed her singing and that he also saw her at Mars Lounge. He revealed that their mother was angry at him for not bringing her back then, but since he used to dream of being a musician and seeing Tuesday that alive while singing, he desired for her to fulfill her dream. Spencer then told Tuesday, that he will be helping her escape and held the AI robot, who tried to stop Tuesday from leaving the house. He then watched with joy Tuesday's performance at Mars' Brightest Competition.