Unlike many rom-coms that drag out the "will-they-won't-they," this manga starts with them already together. The progress is found in their emotional intimacy and small domestic victories, like cooking together or going on "dates" within their home.
If you are looking for battle manga or complex world-building regarding the demon realm, you might find this a bit thin. It is very much a "slice-of-life" story first. they enter a contract of marriage.
The plot kicks off with a lonely protagonist, Theo, who attempts to summon a devil to end his solitude. Enter Helvi, a powerful high-ranking devil who is—contrary to expectations—incredibly adorable and affectionate. Instead of a soul-binding contract of servitude, they enter a contract of marriage. they enter a contract of marriage.