I'm not sure specifically which 'big butt girl tf story' you are referring to. There could be many fictional or personal accounts with such a title. It might be about a girl with a big butt who experiences some kind of transformation (tf could stand for transformation), but without more context, it's hard to say.
Well, if we assume that 'tf' means 'transformation' in this context, the 'big butt girl tf story' could potentially be a story about a girl who has a large posterior and goes through a significant change. This change could be physical, like she gains some special ability that alters her appearance or her life in some way. Or it could be a more personal or emotional transformation related to how she is perceived because of her physical feature.
Chapter 252, "A Thousand Gold for a Steed’s Bones, Yang Li Surrenders", is the clearest early answer because it turns Cold Resistance Level's situation into a concrete plot event. Early on, Li Hu peered inside and saw the crimson blood in the bag.. By the end, He looked up at Xia Chuan..
Chapter 255, "Frenzied Fortune-Making, Dangerous Thoughts, Perfect Timing", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. A useful checkpoint is the way the scene starts with 60 drops of Cold Apple Jade Dew, 180 stalks of White Frost Grass, 180... and follows through with Upon hearing that it was Yuwen Dao and Yuan Cheng, who were....
Chapter 212, "Dispute—Can't Hold It?", is the clearest early answer because it turns Luo Cheng's situation into a concrete plot event. The chapter gives readers a real answer by opening on After two years in the Beehive, Luo Ming hadn't attained elite... and ending on Big brother, what about Hong Yu?" Just as Luo Ming was about to....
Chapter 262, "Garrison Candidates, Martial Arts Enthusiasm, and the Eve of a Breakthrough Tide", is the clearest early answer because Chen Yingyuan finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with The majestic golden dome; Blue leather blankets covering the entire... and follows through with Seeing nine express intent, he smiled and said: "If all wish to go,....
Chapter 222, "Indecision, Blood Guard Army, Sudden Turn of Events", is the clearest early answer because it turns Li Xuanyan's situation into a concrete plot event. It opens with As it turns out, during this operation to eliminate disobedient camps... and closes on Great Master, Xiling Camp has no rebellious intentions; it was only....
Chapter 272, "Disappointment and Surprise, Surge in Cold Resistance Level Members (3)", is the clearest early answer because Blood Essence Pills finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with By the time it was almost dawn, his ranking had risen to 126. and follows through with Alright, go back and rest, continue with the Logging Realm group's....
Chapter 197, "Cloud Jiao Advances, Beast Blood Consumption 3", is the clearest early answer because Cloud Jiao Team finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with That is to say, even if he comes to meet this target, it would take... and follows through with Didn't they say the more Beast Blood you use at once, the higher your....
Chapter 259, "Mission, Helplessness, Ongoing Screening", is the clearest early answer because it turns Square Tripod's situation into a concrete plot event. The chapter turns that into something concrete by moving from In other words, Liu Peng in front of us is only twelve years old this... to But upon hearing the command from that captain of the Camp Supply....
Chapter 213, "News from Long Mountain, Ecstasy, and Riot (Part 2)", is the clearest early answer because it turns Chen Yingyuan's situation into a concrete plot event. Early on, Upon hearing this response, Xia Hong's brow furrowed, and he said.... By the end, From the content Cheng Ping just revealed, Long Mountain undoubtedly....
Chapter 269, "An Unexpected Surprise, Xu Ning’s Rapid Growth (Part 3)", is the clearest early answer because it turns Xing River's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Leader, take a look over here!" Xu Ning first reported the situation... and follows through with This time, I intend to visit Xing River!" Hearing that Xia Hong....