I am going to go out on limb or whatever and say that the cover/back cover of the booklet is in reference to lyrics in Shuukyou.
Someone please give me a tasty sweet.
What I really desire is poison. You know I’m only kidding.
If possible I’d prefer the sweets,
because I think about drinking tea. I don’t mind the cavities.
The tasty sweet is wagashi which is pictured on the back of the booklet, and then of course the cup on the front is a tea cup. Also, the pattern on the tea cup and saucer is of chestnuts.