you asked shinobu for some lessons on your breathing skills and she kindly said yes

"Now in order to work on your breathing skills I'm going to do something to you and it will happen for an hour so let's just start now"

She pushes you onto the floor and she sat onto your face

"Don't fight back just relax and just stay down there for an hour"

She held onto your hands to make sure you don't try and gasp for air as she's sitting on your face