Took me a long time to realise... they aren't having sex of any kind. The girl even says "It's not what it sounds like" in the leftmost panel, she's just receiving a massage so she makes weird gasping sounds. Makes the most sense if you look at the parent pictures as well. Edit: yes, a very sexually suggestive and pleasuring massage. The point is to bully her and put her in an awkward position with the person on the phone
Took me a long time to realise... they aren't having sex of any kind. The girl even says "It's not what it sounds like" in the leftmost panel, she's just receiving a massage so she makes weird gasping sounds. Makes the most sense if you look at the parent pictures as well. Edit: yes, a very sexually suggestive and pleasuring massage. The point is to bully her and put her in an awkward position with the person on the phone
There are a few problems with this theory:
Zui's panties are pulled down.
There is a /\/\/\ high up on Zui butt, suggesting a hip thrusting or recoiling motion, unrelated to what Kaga's hands are doing.
If the artist wanted to suggest merely a massage, why did he pose them in doggy style?
Conversely, the only thing suggesting against sex is that Kaga's skirt is not raised (futa), nor is there apparently a strap-on over top of it.
There is a /\/\/\ high up on Zui butt, suggesting a hip thrusting or recoiling motion, unrelated to what Kaga's hands are doing.
If the artist wanted to suggest merely a massage, why did he pose them in doggy style?
Conversely, the only thing suggesting against sex is that Kaga's skirt is not raised (futa), nor is there apparently a strap-on over top of it.
Kaga is essentially playing a very cruel prank on the Shoukaku sisters. As you note, her skirt isn't lifted, and she isn't wearing a strap-on. Basically she's dry-humping Zuikaku from behind, using the rhythmic impact and targeted massage to make Zuikaku emulate the sounds she might make were she having sex. Everything is intended to make the sounds as suggestive as possible.
The tape on Zuikaku's mouth in the prior images was likely to make sure she could not call for help until Kaga was ready to call Shoukaku on the phone.
Looking at the source there are two comic pages so maybe those could clear this up
It'd help if there were a translation request, but the second comic page almost looks like Kaga is basically trying to justify herself for what she's done.
Which is just fucked up, but let's see if somebody can translate.
It's not what it sounds like...Zuikaku?!It feels so good <3Sho-Shoukaku-neeHaaOh no--HaaAhh...