Shindou-san no Yuuutsu: Toki o Kakeru Otome

The stage is set one year after Yuki's ending from "Sakurayuki". Obviously, Kenji and Sakura are still madly in love. But Shintou is still lonely. Who'd have expected him to warp through time and arrive in the past!? A past in which Kenji and Sakura haven't started dating yet.