The Happo-Fire Burst Scroll was an old scroll which Happosai wrote the secret to his Happo-Fire Burst technique in. After using the Happo-Fire Burst to foil a trap which was meant to end his life (at the cost of a Brassiere), Happosai decided to seal the scroll away so that neither he or anyone else could harm innocent undergarments.
Whilst training Soun and Genma, Happosai began robbing a village multiple times. The villagers soon got tired of this and devised a plan to kill Happosai. When Happosai next robbed the village with Soun and Genma, they used a large boulder to escape, but as Happosai runs off he notices that someone has left a Brassiere on the ground. Happosai's perverted tendencies soon take over and he jumps off the boulder to grab the Brassiere, forgetting about the large boulder which is hurtling towards him (which Soun and Genma are still atop of).
When Happosai remembers about the boulder, he quickly decides to use his Happo-Fire Burt in order to destroy the boulder. Unfortunately, the ensuing blast also damaged the Brassiere. Distraught, Happosai decided to seal away the scroll to his technique so that no more defenceless undergarments can be harmed by the technique.
By the time of the events of the series, Happosai had long forgotten the secret of the technique and maintained his wish not to use it ever again, until his pupils anger him so much that he sees the only way to teach them is to use the technique. Unfortunately, despite remembering the steps to the technique, Happosai still can't remember the secret of the technique, rending it useless.
After travelling to the Wilderness of Japan, Ranma, Soun and Genma discover that a hot spring has sprung up around the location of the buried scroll (in the anime the hot spring was present at the time Happosai buried the scroll). Eventually the trio the scroll, but are unable to read the coded writing Happosai used in the scroll. The group then devise a plan to get Happosai tell them what the scroll says, but even Happosai finds himself unable to remember how to decode the scroll, causing him to rip it up in a fit of rage. Shortly after this, Happosai remembers the secret of the Happo-Fire Burst and begins using it to get revenge of his pupils.