Harukeki Kawa no Nagare ni Nosete

Main character receives a prophecy that he can't return to his home town. But with his father's death on a snowy night he goes there and falls into the river on the way. He wakes up in care of twin sisters Rico and May. Why do these girls live isolated in the mountains? Protagonist has to stay there until full recovery. He has enough time to reveal this mystery.

[From vndbreview]