What makes Rain (Sid song) by SID notable?

'Rain' became notable for its inclusion as the theme song for the popular anime series 'Black Butler', which significantly broadened SID's audience. The single also showcased the band's ability to blend emotional depth with catchy hooks, contributing to their ongoing influence in the J-Rock genre. Released on June 2, 2010, 'Rain' marked a significant moment in SID's career as their fifth single following the successful 'Kagayaku Tsuki no Yō ni'. At this point, the band had already established themselves as a prominent act in the Japanese rock scene, building on their previous commercial success and solidifying their fanbase.