Mermaid Forest - 1x01 - Mermaid Does Not Smile- Followmy.tv

In a mountain village, inhabited half by identical young women and half by identical old women, live two unique individuals, Mana, a girl who has just turned fifteen, and Baba (Nanny in the English dub), the old woman who pampers Mana while keeping her shackled in bed. The secret the women keep, even from Mana, is that all the identical women are mermaids and that aged mermaids need to eat young immortal women to regain their youth. After Baba feeds the flesh of one of the mermaids to Mana, Yuta learns about their ultimate plan for Mana and tells her about it. While trying to stop Yuta and Mana from escaping, the women revert to their mermaid form and are unable to take human form again. Baba, also an immortal human, stays behind as Yuta and Mana leave. Yuta tells Mana that life as an immortal isn't all bad, but he still hopes to become mortal again.