"Shuāngxiàng Xìngfú" is the fourth song of the Bidirectional Series and it features Luo Tianyi and Yuezheng Ling, whose voice is provided by Chinese VOCALOID3, YANHE. An alternative ending where Ling knew her actions in declaring war on Tianyi may eventually hurt YANHE. As a result, she stops Tianyi from murdering him and informs her that it was all her fault and she leaves, allowing Tianyi and YANHE to be together. After Ling received her own voicebank in 2015, her vocals were used to sing the song in the album, Shuāngxiàng·Lúnhuí yǔ Xìngfú (双向·轮回与幸福).