Well, you're right, it's strange that the drug's effect hasn't disappeared by the end of the chapter. It will probably still be in effect in the next chapter, which would be great.
Besides undressing of her own free will, she was driven by jealousy (she also let him touch her breasts of her own free will, I think all that's left is for them to kiss).
My comment has nothing to do with this chapter, but I went to Twitter and saw a post from nyaromeron where it seems that a busty RyuRyu will appear in the next chapter.
I find it curious that Sachio could identify the mother just by her silhouette and voice, but to discover Kaneda's identity she needed to feel her breasts. This leads me to believe that Sachio is only interested in Kaneda's breasts, not in Kaneda herself.
Since this chapter was about Sachio X mother Kaneda, nyaromeron decided that next month's chapter will be about Sachio X mother Tetoko (he just uploaded a preview on his twitter)
For the first time, I felt jealousy towards a character in this manga, and it's the guy who drowns in Tetoko's tits in the final panel. Please nyaromeron more appearances of Tetoko with breast expansion.
There are two Sebastians present, and neither does anything to stop their mistress from being stripped and groped. Perhaps the Sebastians resent Kaneda for everything he puts them through, and that's why they do nothing when Kaneda's melons are grabbed.
This comment has nothing to do with the chapter, but I went to Nyaromelon Twitter and it seems that the editor did not have time to verify in detail the content of the following chapters, so the chapters did not have corrections and will be published without any restrictions that they always put...
I think this is the first time Kaneda has consciously, without any incident, used his body to show off/ride someone. I also thought he wasn't aware of the libido he provoked in Sachio.