あの橋に誓って (Ano Hashi ni Chikatte)

Background
Elluka Clockworker, along with the other Three Heroes, Mariam Futapie and Leonhart Avadonia are going to the Sanosun Bridge to swear their alligence to the King of Lucifenia, Arth Lucifen d'Autriche. While Elluka thinks about how bridges conects people's hearts aswell as countries, she sees a bat in the sky and hears it sing the Clockwork Lullaby. After the four meet up at the bridge, they swear their loyalty to the country.

This song was released on Lucifenia Trinity.