Sankakkei no Kowashikata

Koto, Aya, and Erika were secretly in love with each other.
Koto revealed her feelings for Aya, but a short while later, Aya disappeared as if she had been spirited away.
Seven years later, Aya reappears to Koto and Erika, just as she was then...
(Source: U-Next, translated)