Sprite

Yoshiko is a hardworking high-school student whose free time is almost entirely taken up by attempts to help out a hikikomori childhood friend and an odd, reclusive uncle.
While on a visit to her uncle's penthouse with two of her friends, Yoshiko notices a black substance that resembles snow beginning to fall from the sky -- but her friends see nothing. Soon afterwards, a massive earthquake shakes the city, and Yoshiko, her friends, her uncle and his dog, all find themselves trapped in a strange world they do not recognize...with an assortment of weird people to keep them company.
• Volume 6-7 contain 4 chapters manga of the same name Sprite, published in Big Comic Superior 2002 #20-23. This prequel tells a story of Fuyuko and Shingo.