It was better than I expected. The voice actress for Tomoko the mom was fantastic.
However, I was hoping they'd go past the manga and have a scene with the mom & the guys at the end but I guess not.
These are exactly my thoughts!
I read the manga after watching the animation, there are a few things that should have stayed, like the clothes during the scenes. But like you said, the most wasted oportunity was the potential gangbang. But I must say the voice actress was sooo fantastic.
In the manga the mom seemed a bit like a quirky airhead but in the animation she was this cool levelheaded mother that was not going over the top during sex like in other hentais. I prefered her in the animation, especially when she hears how she is fucking her sons bully. The cuts between the scenes was also great eventhough it is only 16 minutes long.
Normally Hentais don't work for me because the voice acting is often over the top but this was a pleasant suprise.
I really wish there were more manga / hentais like this, the mother gets tricked into fucking the bully and hates it afterwards. No mindbreak, no slut, just anger, regret and powerlessness.
The only thing that is like this is of course the legendary [Yojouhan Shobou] Ikenie no Haha | Sacrificial Mother but other than hat no luck.