Aru Hi, Mukuchi na Konyakusha no Kanjou ga Wakaru You ni Narimashita

Ashe, the daughter of a baron, was expected to be rejected at an arranged marriage meeting, but as a result, she is engaged to Bernhard, the third son of the Count of Estholm. As she tries to deepen her friendship with the extremely quiet Bernhard, she notices that the flower on his chest is changing shape to match his feelings. A pure love story begins, where a mystical flower connects the two lovers! (Source: Kodansha, translated)