The Silver Thread (The A’aru Legacy #1) by Ema Arden:
 
Alderian is an A’aruin, a guardian spirit bound by a luminous Silver Thread to Augustine, the human he has watched over for lifetimes. Their connection is eternal, yet cruelly distant: each is fated to forget the other, never to meet in waking life. But when Augustine wakes from a dream remembering Alderian’s name, the ancient Law of Oblivion fractures.
 
Suddenly, she can see the Silver Threads linking every soul to its guardian. For Alderian, this breach is both hope and terror: if the High Council discovers their anomaly, both could be erased from existence.
 
As Augustine’s new sight draws Shadows and danger, she must navigate a world where her classmates are not what they seem and her own heart is torn between the impossible love for her guardian and the ordinary life slipping away.
 
In a world where memory is forbidden and love is a risk, how far will two souls go to reclaim what was once lost? "The Silver Thread" is a sweeping tale of forbidden love, open door romance, spiritual rebellion, and the courage to choose destiny over fate.