Arikitari Heroes is an original song featuring Hatsune Miku, GUMI, Kagamine Rin, and MAYU. It is the fifth song in the Bookmark of Demise Project. It can be interpreted as an answer song to the four earlier songs in the project, because it contains events from those songs. Events include A-ya playing hide and seek alone, C-ta's murder of A-ya, D-ne's imitation of B-ko, and A-ya and C-ta's childhood memories. After getting a couple words from each participent in the Demise Game, it opens upon the group play Kokkuri-san to summon the Bookmark of Demise.

(Source: Vocaloid Wiki)