For this color manga, Oono obviously liked this outfit of Kei's by Kimura Takahiro in the artwork for the stereo drama, Tenshi no Yasumi
(left) High Five! End of the last mission; last caption (roughly): "Together, they can begin to bring about limitless possibilities."
(right) self-portrait of the artist; Oono 'Takemaru' adopted her nom de plume from her cat, shown here...