I'm tagging Fuusuke as the artist for the ぶいすぽっ！年末カウントダウン2024 (https://event.vspo.jp/vspo-countdown-2024/, https://store.vspo.jp/collections/vspo-countdown-2024) illustrations.
I don't think the artist has been confirmed anywhere, but the roughness/texture of the line art, the coloring, the head shape/hair/eyes/eyebrows/eyelids/nose/mouth/chin shadow, all match Fuusuke's art style IMHO.