シアワセうさぎ (Shiawase Usagi) is a Touhou Project vocal arrange track that entered maimai during the GreeN PLUS update on August 22, 2014. Performed by amane and beatMARIO under the doujin circle COOL＆CREATE, the song is built from two ZUN originals, Tewi Inaba's stage theme お宇佐さまの素い幡 (from 東方花映塚 ～ Phantasmagoria of Flower View) and the stage 5 theme シンデレラケージ ～ Kagome-Kagome (from 東方永夜抄 ～ Imperishable Night). The arrangement was handled by myu314, a composer who was formerly part of COOL＆CREATE. The track first appeared on the 2007 album 幻想メガ★ラバ, released by the circle PROJECT tM@S at the 博麗神社例大祭 (Hakurei Shrine Reitaisai) as a book-included CD. Its lyrics contain a playful homage to IOSYS's well-known Touhou arrange "魔理沙は大変なものを盗んでいきました." Shortly after シアワセうさぎ's release, the same combination of original themes was used by IOSYS for the companion arrange "ウサテイ," creating a paired relationship between the two songs. In maimai, the song has undergone several difficulty rebalancings across versions, its Master chart, originally rated level 10, was raised to 11 during the UNiVERSE+ era, and the Advanced chart rose from 6 to 7 in FESTiVAL, reflecting the game's evolving difficulty standards for older tracks. The Expert and Master charts were designed by はっぴー and 某S氏 respectively. The jacket art originally used the とうほう☆あまねりお album cover (released December 30, 2013 by COOL＆CREATE) before receiving dedicated jacket art in maimai PiNK.