The Holy Grail of Eris, Vol. 6 (light novel): Amethyst Fate

It's been over a year since Daeg Gallus’s plot rocked the kingdom, and Connie and Randolph are finally preparing to get married. But as the date approaches, Randolph grows strangely cold, and Scarlett’s behavior becomes increasingly erratic. Meanwhile, Connie, now working for Abigail as a detective, winds up entangled in a major art forgery case involving a dangerous marquess. With her wedding plans floundering and Scarlett MIA, how is Connie supposed to cope?!