i think it is pretty simple to understand how tribbing works, unless you have never come in contact with anything concerning female anatomy, so i would think futanari is the simplest explanation, but that is just me. there is a ton of yuri pairings that you see with futa on pixiv anyway
At first I thought they were at Mr. Donut.... but then I looked again and thought they were ripping a whole into another dimension while kissing....and finally I realize she's holding a role of tape and they are preparing for the school festival....wow... I'm either really creative or really stupid.