18+ Ayame-senpai wa Boku to Himitsu no Keiyaku wo

On his way home from school, Daiki Mitsuyaーan ordinary high school student finds a girl covered in wounds. Upon closer look, he finds that the girl has animal ears, but she licks Daiki's ears and leaves. Daiki begins to wonder if it was just a dream, when Ayame Sakuragami appears upon him...? After telling her of the ability of Daiki's ears, Ayame feels responsible for dragging him into this, and proposes an oath of absolute servitude to protect him at all costs!

(Source: Takeshobo, translated)