This song article is lacking a proper background. You can help by adding one! The relevant section in the Song Article Guideline is a good starting point, and this blog post may also be helpful. We apologize for the inconvenience this may cause in the meantime.
Song pages lacking proper backgrounds are automatically sorted into this category.
"Yakusoku" is an original Japanese VOCALOID song by Yama△ featuring Megurine Luka. It is featured in his album Laboratory. A remastered version of this song is featured in Hitoshizuku-P × Yama△'s first major album EndlessroLL.