Oshino informs Senjogahara that he won't be able to cure her problem, but that he will be able to help her. Senjogahara distrusts him at first, saying that she can't believe he would simply be doing this for free. Oshino says that he'll charge her 100,000 Yen if it makes her feel better, and Araragi complains that is a hell of a lot less than Oshino charged him (4 Million Yen) for his problem. Oshino says that was his vampire fee, and also that he charged 100,000 Yen to help his friend Hanekawa fix her own problem.
Senjogahara goes back to her house to shower and get changed, and Araragi follows her home. She parades her body around in front of Araragi, and puts on her clothes very slowly while making sarcastic comments about Araragi's insecurities and his virginity while he can do little but complain back. Eventually, the two of them return to meet Oshino who has dressed in the robes of a priest. He says that he's not actually a priest, but he did study theology in school. Oshino leads them upstairs to a makeshift shrine, saying that he can't exactly remove Senjogahara's problem by himself, that's up to the Crab. And because this Crab is a God, Senjogahara needs to ask it nicely to give back her weight, and has to mean it in her heart.
The three of them start praying to the crab god, and Senjogahara regales us with a tale of her past (which Araragi further narrates in flashback mode). Her father died in an accident and later Senjogahara needed surgery. Her mother didn't think she'd make it, so she joined a cult for the emotional support they offered her. Somehow, Senjogahara survived the surgery and went home, but the mother stayed with the cult. One day, the mother brought home one of the higher-ups from the cult who proceeded to try raping Senjogahara, but she fought back with a spiked heel and stabbed the man in the face while the mother simply watched and did nothing. Some time after that, the mother died, leaving Senjogahara all alone.
Senjogahara makes a tearful plea to the Crab God to give her weight and her family back. The Crab God takes shape in the middle of the room, visible only to Senjogahara, but then pins her to a wall and starts strangling her. Oshino grabs the invisible crab and starts trying to break it up, but Senjogahara decides to reason with it again, and the Crab God decides to give her weight back. Not just physically, but also the symbolic weight of her emotions, to the point where she stops making snide comments about Araragi and actually asks him to be her friend.
Araragi later returns home and tries to get some sleep before school, but is immediately jostled awake by his sisters, finding that morning has already come. He claims that he feels strangely heavy, and stands on the scale to find that his weight has mysteriously doubled from 50 kg to 100 kg, possibly because of that Crab God.