Hitohira no Koi ga Furu

A superstition at Haruru's school claims that a couple who sees the bullet train at 6 am will remain together forever, while seeing it at 10 pm will cause them to break up. Haruru is in a new relationship with Nagi, a boy from another school. Their relationship is just beginning when Haruru unexpectedly sees the 6 am bullet train with someone else, setting off the effects of the jinx.