Since there are so many people who seems not to understand when I'm talking about Kobayashi looks like Go-on Yellow,
Aizawa Rina (Go-on Yellow)
And Kobayashi Ryoko (Maou's Libarian)
Both are taken from the official website.
Last, Go-on yellow,
Personally I still prefer Go-on yellow, because that kobayashi girl looks uglier in Maou while Go-on yellow looks cuter in Go-onger.