Look, Master! Boobs!!
English title: Look, Master! Boobs!!
Japanese title: ご主人様おっぱいですよ!!
Circle: TOYBOX and Kujira Logic
A compilation of two stories:
In the first one, Caster is annoyed that her Master is too beta to make a move on her, despite being obviously attracted to her. So she decides to tie him up and use her boobs to squeeze the beta out of him.
In the second one, Caster want to put her Master in high spirits before the final battle. He takes up on her offer and asks her to use her boobs to squeeze the tension out of him.