Mascot characters of コルゲンコーワ (Colgen Kowa), a cold remedy brand of Kowa Company, Limited. (Danbooru romanization: Kouwa Company) Aka. コーワのカエル (Kowa's Frogs). Kero-chan is a girl frog, and Koro-chan is a boy frog. You can find their statues at almost every Japanese pharmacy front.