There's a Demon on the Radio (Alastor Male Reader x Highschool DxD)

Rias's cousin, son of Zeoticus's late brother. An immensely powerful Devil, he loves old human radios. He even has had one placed in as many places in home around the Underworld, where he broadcasted his feats against those who've tried fighting him. He was soon given the title, the Radio Demon, feared across the supernatural world.

What happens when he hears of the arranged marriage between his adorable cousin and the sick head Riser Phenex? Boredom relief!