The series contains 2 volumes;
1) Vartrag Tale
Ralph can see angels and demons. When he was five years old he came across the winged demon Valafar and was completely charmed by him. He made a pact with the demon in order to make his wish, to live with Valafar, come true. Seven years must pass, and there are two conditions that must be met for the pact to be fulfilled. Can the older Ralph discard his ties to humanity and fulfill the pact...?
2) Vartrag Tale - Korumajou no Shitsuji