There was something about Genma which really rubbed Nabiki the wrong way. It had only been a few days since he had dragged his son to their house, and conspired with her father to force an engagement. And her opinion of the man did not improve over time.
That was why she was taking advantage of the father's visit to a nearby bar to thoroughly search Genma's belongings. The latex gloves she had appropriated from the school's chem lab weren't worn to protect her from leaving fingerprints as evidence, but because it was obvious that Genma had not been overly concerned with the hygiene of his laundry during his travels.
When she had found, and read the photocopy of the seppuku contract, she hastily restored everything else to its original state, and hurried off with the evidence.
It was difficult to arrange, but she managed to convince Kasumi to send Genma out of the house, while making sure he didn't send his son in his place, or take Soun along for company. Nabiki managed to gather her family plus Ranma in the living room to meet behind Genma's back without him noticing. "I found something that is vitally important to both our families."
Upon reading through it, which didn't take long, Soun started wailing, while Ranma stared off into space, shell-shocked.
Akane murmured, "I can't believe he'd make a seppuku pact."
"You're wrong! It only looks like a seppuku pact." In order to get his full attention, Nabiki barked, "Ranma!" Continuing in a normal voice, she asked, "You write your name at the top of every homework assignment, don't you? If I tricked you into signing a contract to hunt down and kill your father, by disguising it so you thought you were signing your homework, then you wouldn't be legally bound or bound by honor to do it, right?"
"Well, no. No, of course not."
"Your signature on the contract is only important if you knew what the contract said before signing. Putting aside the question whether a five year old boy could understand seppuku, it is obvious from looking at the contract that you were finger-painting."
"But Ranma's father signed it. That means that Ranma's bound to it by family honor."
"That's the important point! Putting aside Genma's promise to kill himself; Ranma's father signed a paper stating that he would kill Ranma or compel him to kill himself. This isn't a seppuku contract; this isn't an agreement involving honor. This is evidence of conspiracy to commit premeditated murder."