Konyaku Haki wo Neratte Kioku Soushitsu no Furi wo Shitara, Sokkenai Taido datta Konyakusha ga "Kioku wo Ushinau Mae no Kimi wa, Ore ni Betabore datta" to iu, Tondemonai Uso wo Tsuki Hajimeta 

Viola, the daughter of a viscount, is engaged to Philip Laurenson, the charming and popular heir to a duke. But the two are far from a match, and their silent tea parties do little to help them bond. In a desperate bid to escape the engagement, Viola feigns amnesia after a minor accident. However, Philip's reaction is not at all what she expected, as he starts telling her how much they used to love each other and how she used to call him..."Phil"? Which is far from the truth! And yet, from the brink of a crumbling engagement, a romance begins to blossom between the inexperienced lord and the oblivious lady.
(Source: Manga UP!)