Tomoe Kirinokojima is a jaded young man who doesn't believe in love or happiness. Aine, on the other hand, is a genuine angel come to Earth who uses her magical guitar to sing love's praises to sooth the broken hearts of couples in love. One day during archery practice, Tomoe shoots Aine out of the sky and ruins her guitar which is powered by the red threads of fate--threads said in myth to bind two lovers together forever. With only one thread left, Aine is left powerless to help those in need. As luck would have it, Tomoe is able to use this final thread in his bow to act like a real-life cupid.
Like it or not, Tomoe is roped into helping Aine on her mission to help the couples of the world. Will Tomoe have a change of heart, or will his apathy rub off on Aine? There's only one way to find out...