Akuyaku Reijou no Okiniiri: Ouji...... Jama

Iris, the "Wise Princess Who Never Smiles," had her memories of her reincarnation come back to her. She discovers that Fiona, a princess of a neighboring kingdom, is her from a former life, and that she is in danger due to Prince Alvin's betrayal.
Iris goes to the neighboring country as the princess's educator to save Fiona, but an obstacle stands in her way in the form of a cool-headed prince who has no sense of tact. So unfolds the love between a wise princess who never smiles and a cool-headed prince.
(Source: Tokyopop)