期待已久的第四张Vocaloid单曲《Contrail》终于发布在这张单曲中，IA担任主唱，铃木津美提供和声。标题曲《Contrail》围绕“继承”主题，是一首忧伤却节奏明快的摇滚曲。B面曲目是2011年作品《A Flower Blooming in the Desert》的重制版，名为《Orange Horizon》。The long-awaited 4th Vocaloid single,"Contrail," is finally released after about three months!This time, IA takes the lead vocals, with Tsudumi Suzuki providing chorus. The title track, themed around"inheritance," is a melancholic yet fast-paced rock tune.The B-side features a remake of the 2011 track"A Flower Blooming in the Desert," titled"Orange Horizon."