That was an uncomfortable chapter. It's a shame because I feel the story was trying to show Marika couldn't resist temptation and then admitting this when she said she wanted to also make Aya feel good. That'd have been fine if they just had Mirake internally wrestling with herself rather than her actually saying no which I am guessing the point the the writer was trying to put across but the execution has been horrible and ended up turning this it into something that's hard to look past.
Flicking through the comments, I never knew he also wrote 'There's no way I could have a lover', I remember dropping that manga as well as it also had a disturbing scene.