Oops! Just noticed one of the thumbs above was this angle. Never mind this one!
An excellent place to try your luck would be at Miharu Izawa's comprehensive Sougouwikifilmography.
Another clue is that the movie's theme has to do with drugging the victim, in this case, probably within a mother & son setting. (I have already gone through her starring roles.) So the best bet would be a multi-actress and multi-episodic movie, such as DANDY-163 (which the actress appears in, but that's not it). Seemed to me that a cover showcasing sleeping women would serve as a short-cut to success, but I did not notice such a cover.