Sangatsu no Phantasia is a J-pop music unit featuring vocalist Mia, with music videos and promotional images created by various artists. They started in 2015 by sharing their song “Day Break” on social media before making their major debut in 2016 single “Hajimari no Sokudo,” which was used as the ending theme for Kiznaiver. They followed this with second single, “Gunjō Sekai” in December of the same year and “Fairy Tail,” which became the ending theme for Interviews with Monster Girls in February 2017, seeing debut album, Ano Toki no Uta ga Kikoeru, appear just over a month later. Over the next few years, they continued to release more popular theme songs, including “Rubicon,” (2017) (ending theme for Re:Creators) “Kaze no Koe o Kikinagara/Collage,” (2018) (ending theme for Slow Start) and “Pink Lemonade,” (2018), (opening theme for As Miss Beelzebub Likes), with second album, Girl's Blue, Happy Sad dropping on the same day. In 2020, their third album, Blue Pop wa Nari Yamanai, dropped on September 30, followed by seventh single, “101/Yakō,” (opening theme for The Honor Student at Magic High School) in 2021. Their third album, Kaikou Shoujo, appeared the following year, with EP Golden Ray - Kaitai Shinsyou appearing in September 2023, which reached number 38 on the Japanese charts.