Little is known about SUNNY'S DAD, as he is only mentioned passingly and never shows up in any meaningful capacity. At some point, he married SUNNY'S MOM and had a daughter, MARI, and years later a son named SUNNY. They lived in a house in FARAWAY beside KEL and HERO's house. It is unknown what his job was, though he is said to have needed a laptop for work.

SUNNY notes various things about his father, such as that he gave SUNNY his computer, that he took his family on vacations and collected souvenirs, that he and SUNNY'S MOM collected books which were "gathering dust," that he sleeps on the right side of his bed, that he grew bonsai trees, that he and his wife didn't allow SUNNY to look in their wardrobe, and that he watched TV but got mad when the remote went missing.

In the PHOTO ALBUM, BASIL's annotation of a photo of HERO and MARI sleeping together on the couch notes that "MARI's dad might be kind of mad if he saw it," implying that he may have been disapproving of MARI and HERO's relationship.

After MARI's death, he was the one to cut down the tree from which her body was hung. This is implied in one of the letter segments in HEADSPACE, in which a black outline of SUNNY'S DAD is shown continuously chopping at a tree. This same segment has SUNNY'S DAD claim that SUNNY is not his son, though whether this is something he actually said or something SUNNY imagined out of guilt is unknown.