The Snake Girl And The Silver-Haired Witch - 1968 - 6/10
AKA - Hebi Musume to Hakuhatsuma // 蛇娘と白髪魔

Sayuri is being adopted. By her own parents!
Owing to a mix-up at birth, another child was switched in her place.
No matter, now she has a big sister.
Who is completely alarmed about being displaced by the blood child.
Sayuri cannot help but notice the mask her sister wears, and – wait – is her back covered in scales?
She soon realizes her sister is a snake, in league with a murderous witch.

Horror gem boasts frightful costumes, wild optical effects, and hundreds of snakes.
Locked rooms, experiments in the basement, a mother losing her mind add to a complicated plot.
A bit campy now, though I wonder if children saw this during its run.
I can imagine it unsettling them.