It seems Yukino grew a spine & decided to bleach her hair to go with the new image :P ?

But what is this about, and who are the other people? And moreover, why's there a giant Gundam peeking through the window in the upper left corner?

err, right. Right corner. Curses remembering things like the south and north & left & right.

This is from one of the Future GPX Cyber Formula games, the characters were designed by Hirokazu Hisayuki who also did work for GEAR Fighter Dendoh and Mai-HiME. The series is about racing super cars designed by Shoji Kawamori, and was rather influential on anime in the early 90s, G Gundam in particular.

This is not Mai-Hime/Mai-Otome and that is not Haruka. The character designer just reused the design.

Obviously.