Tenmon Dokei no Aria

In the world of Tenmon Dokei no Aria, nobody knows or remembers who built the mysterious clock tower. Legends say that whoever hears the song of the clock will be happy forever. Then one day, protagonist Taiga hears aforementioned song and when he climbs the tower he finds a girl named “Aria”, a young girl who claims to be the one to bring you happiness.

But in the end it appears that she doesn’t even understand what happiness is. She decides to stay with Taiga in order to learn about happiness, and so begins her school life together with Taiga, throwing away her immortality in the proces…