butterfly manji maru

When I was 5th grade, my friend called me to the apartment where he lived, saying, "I can jump from the second floor of the apartment and land with my legs stretched out!"
Upon arriving at the mansion, he jumped from the second floor with his legs stretched out.
Phan! !! He landed upright with a high-pitched plosive that sounded like a cracker. And he fell forward with his knees extended.
The next day he had a crushed fracture in both knees and was in a wheelchair. The next week, for some reason he had a broken arm.