Kuzu no Honkai

Mugi and Hanabi are the perfect high school couple...but their relationship is built on a single shared secret: They're each in love with someone else.
(Source: Yen Press)
Note: Includes one extra chapter and the one-shots "Nyan Nyan Prelude", "Nyan Nyan Serenade", "Nyan Nyan Oratorio", "Nyan Nyan Cantata", and "Nyan Nyan Andante".