Her face and voice didn't match. This incongruity is good.
Her sloppy, ecstatic face, like she's gone crazy from masturbation, is a work that could only have been filmed in this era.
If Chikako were filmed now, she would probably still be a cute girl.
Her nails are sparkling and it's so naughty when she spreads her legs. Those labia are quite something too.
She opens up so you can see her vaginal opening clearly, it's really lewd. It's fine to masturbate with those nails, but
I want her to feel more. I wanted to see her twitch and show her perverted side.