Even though the FANBOX page doesn't specify oky/Okayu in the gallery title, unlike their other hololive-themed galleries (i.e. mrn/Marine, krn/Korone), this character's overall design is 99.999999% identical to Hololive's Nekomata Okayu, right down to the choker.
Should the tags be added, even if purely speculative?
@lurphysmaw - It's tagged as Okayu on Pixiv (https://www.pixiv.net/artworks/96492915), and honestly I don't think there's any mistaking who it's supposed to be.