Saiyuki chapter 55 – question about the stained glass window?

In this picture, we see two people painted on the stained glass window behind the shadowed figure (Nii), presumably saints. I’m particularly curious about the one holding a book – is it any saint in particular, or is it just there to make it look pretty? Knowing Minekura, I wouldn’t be surprised if it was supposed to be a certain saint, but not knowing much about saints, I don’t have the slightest idea if it is or isn’t. If anyone has any idea at all about what possible saints it could be meant to represent, that would be great. =)