In the story a piece of string, who were the opposing characters and their relationship

The opposing characters are Maitre Hauchecorne and Maitre Malandain, two peasants who had had a quarrel before, and now they enter another dispute. Namely, Hauchecorne found a worthless piece of string on the ground and, being very economical, picked it up from the ground. When he realized that his "enemy" Malandain had seen him, he pretended that he was just looking for something he dropped. Later on, Hauchecorne gets accused of finding a lost pocketbook with money and not wanting to return it. The key witness was, of course, Malandain. This is the main conflict of the story, and it will ultimately be the reason for Hauchecorne's illness and death.

Hauchecorne and Malandain are actually very similar. Both are cunning and practical. Just like Hauchecorne is actually capable of finding a lost thing and keeping it (even though he didn't do it in this case), Malandain is capable of intentionally lying, just to spite Hauchecorne.