Sunday is a Halovian character from Honkai: Star Rail, the HoYoverse game, where he debuted as a playable 5-star Imaginary Harmony character in Version 2.7 in December 2024. Before joining the Astral Express, he was the former head of the Oak Family, one of the ruling households of The Family on Penacony. He is the elder brother of the singer Robin, and the two were raised as orphans after losing their mother in the Stellaron disaster.

He is known for a courteous, philosophical manner and the belief that no gods will save people unconditionally, so change depends on one's own strength. Sources describe him as a seeker of paradise. His path took him from organizing the Charmony Festival to stepping down, taking off the family robe, and joining the Express as a fugitive and a mere passenger. He often speaks in metaphors about stars, the sun and paths.

The person who ends up