What on earth is “Xz”?

A white silhouette of a running figure appears over a large grey object with Japanese characters, set against a background of pink and blue polka-dotted and star-patterned shapes with black speed lines. A girl in a school uniform points forward with her right hand, then closes her eyes and tilts her head back. A girl with brown hair and a red bow sits on a blue couch, holding a small brown animal and smiling. A group of five boys in school uniforms stand in a line, making a synchronized pose with their hands on their shoulders. A shirtless boy with brown hair stands by a swimming pool, making