"Halzion" or "Harujion" (ハルジオン, Philadelphia fleabane) is a song recorded by Japanese music duo Yoasobi. It was released on May 11, 2020 as a digital single. The song was based on "Soredemo, Happy End" (それでも、ハッピーエンド), a short story written by Hashizume Shunki (橋爪駿輝), marking the first time that Yoasobi collaborated with a professional novelist. Unlike the duo's former two songs, the source material was not based on the hosting website Monogatary. Rather, both the song and the short story were released as part of an advertising campaign by Suntory known as the "Immersive Song Project" to promote their new energy drink named Zone. The campaign also included songs by Kizuna Ai and Kaf.