Hikikomori Hakoiri Reijou no Kekkon

The coming-of-age party. It is a party organised by the monarchy to which nobilities who have turned 17 are invited to.
In a corner of the glamorous venue, a mysterious wooden box lays there out of place. The only one to approach the box that's puzzling everyone there was the country's second prince, Cyphon. As Cyphon inspected the box with eyes full of curiosity, that's when a voice called out from within it...
"Excuse me... Is there anything you need...?"
This is a romantic fantasy about a socially inept and (literally) sheltered noble girl and a prince!