Yumiko is quoting the voiceover from the Marimite opening. The actual characters aren’t quite so idealized.

Pouncing on Yumi here is Sei. (You don’t need to remember that. But, for the record, Sei is awesome.)

Heinkel: Timothy, Yumiko used to attend this school. You should ask her about it.

Timothy: Okay! Sister Yumiko, what should I know?

Yumiko: Lillian Girls’ School is a garden for maidens. Their pure bodies and minds are wrapped in dark-colored school uniforms. The pleats on their skirts shouldn’t be noticeable. Their white sailor collars should always be tidy. Walking slowly is preferred here.

Heinkel: Come on, Yumiko…

That’s just what they say in the brochures.

Sei: {Yumi-chan! You can’t confess unless you do a little sinning first!}