Scum's Wish(2012)

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 (Meow Meow Prelude)", "Nyan Nyan Serenade (Meow Meow Serenade)", "Nyan Nyan Oratorio (Meow Meow Oratorio)", "Nyan Nyan Cantata (Meow Meow Cantata)" and "Nyan Nyan Andante (Meow Meow Andante)".