President of the school's disciplinary committee, and secret fan of American superhero comics, she initially gets involved to punish Eiko for the commotion she caused. Eiko, however, becomes convinced that Shiori is her comrade in action, naming her "Blazer Yellow".
However, supposedly in order to put a stop to Eiko's antics, she decides to watch over her. Which means getting involved in the club herself.
And just occasionally she gives off hints that secretly she's enjoying the whole thing.