mc and the saint as children made a promise to date each other when they grow older but when mc sees the saint she was getting married to the hero. I know that it is a manga .
The fiancée of the main character (Wazu) leaves him for the Hero. Devastated, Wazu runs off to a dangerous mountain full of S-ranked monsters. There, he befriends a cute, chibi dragon creature. Also, the voice of a goddess starts speaking to him from within his status card, and informs him that he has a special "Bizarre Eater" skill, which allows him to get stronger by eating anything that is higher ranked than he is.