Yakusoku (2019)
English title: Promise
Japanese title: 約束
Type: Music
Episodes: 2
Source: Original
Studios: Studio Gohan
Duration: 4 min per ep
Rating: PG-13 - Teens 13 or older

The video can be considered a prequel to Saikai.

Similarly, there are two versions of the video that are sung by Hatsune Miku on Niconico, and Harumaki Gohan on YouTube, both focus on a different girl.