Hana, a shy high school girl with a love for books and a heart full of unspoken dreams, never imagined her small gesture would change everything. When she leaves handmade chocolates anonymously on the school librarian's desk for Valentine's Day, she expects nothing in return—only a quiet moment of courage. But Kenji Igarashi, the gentle and reserved librarian, surprises her with a handwritten invitation on White Day. Under the blooming cherry blossoms, a simple cup of tea begins a tender journey of shared moments, whispered hopes, and a fragile connection growing stronger with each passing day. Yet both Hana and Kenji carry their own unspoken fears. As they navigate the delicate path between friendship and something deeper, old wounds and self-doubt threaten to keep them apart. Hana's heart longs to confess her true feelings, while Kenji struggles to let go of a past that once silenced his voice. Can two quiet souls find the courage to trust in a love that blooms from the simplest of gestures? Or will fear keep their hearts forever at a distance? A Promise on White Day is a gentle, heartwarming tale of love born through words, patience, and the beauty of small moments that can change a life.