So, the plot has given us enough clues. Looks like in his past life, ML was a peasant and fell in love with an aristocrat. Then, using a stone, strictly according to the instructions, he tied him to himself with a thread of fate. Judging by the paper that MC found in the archives, punishment for this is all the bad luck that always happens to ML. And here we are, in their next life. And MC is actually destined for that girl, but...
So, the plot has given us enough clues. Looks like in his past life, ML was a peasant and fell in love with an aristocrat. Then, using a stone, strictly according to the instructions, he tied him to himself with a thread of fate. Judging by the paper that MC found in the archives, punishment for this is all the bad luck that always happens to ML. And here we are, in their next life. And MC is actually destined for that girl, but...