Mamiya-san to Issho

Sasara is a strange girl who always responds to love confessions with "Sure, only if you die." One day she was confessed to by the beautiful and popular Mamiya, a third-year upperclassman. Sasara was surprised that Mamiya loves her even though they're both girls, but she responded like she always does. The next day, she found out from her classmates that Mamiya had been a missing person, and realized the one she is seeing now is a ghost. Sasara ran out, cried and said Mamiya is dead because of her, but also smiled because Mamiya had met her condition and proved her love. The two of them started dating. Sasara set out to unravel the truth behind Mamiya's death.

(Source: MU)