- "Triangle -vol. 1-"
"Triangle -vol. 1-" is the first album in the Triangle series, which are given out as promotional albums for buying ¥3,500 or more worth of products. It is a mini compilation album featuring three previously unreleased songs by Yuuyu-P, Uramanbou, and mothy.
This album was only sold in K-BOOKS's stores, no online sales were released.
|1.||"おはようメトロトゥーメートル (Ohayō Metoroto Umētoru)" (Good Morning, Two-Meter Metro)||Yuuyu-P||Hatsune Miku||4:22|
|2.||"交通機関依存型勇者のミラクル文房具 (Kōtsūkikan Izon-Gata Yūsha no Miracle Bunbōgu)" (The Transportation-Dependant Hero's Miracle Stationery)||Ie no Ura de Manbou ga ShinderuP||Hatsune Miku||2:36|
|3.||"待ち続けた手紙 (Machi Tsuzuketa Tegami)" (The Letter She Kept Waiting For)||mothy||Kagamine Len||5:05|