Hitohira no Koi ga Furu

Synopsis

There's a jinx at Haruru's school—if a couple sees the bullet train at 6 a.m. together, they'll be together forever! But if a couple sees the bullet train at 10 p.m. together, they'll break up! Haruru is going out with Nagi, a boy who goes to another school, and their love is just starting to blossom. But what happens when Haruru happens to see the 6 a.m. bullet train with someone else!? (Source: MyAnimeList)