“…An imitation tree. To put it simply, a number of layers of white cloth like a yacht’s sail are formed into the shape of a tree and various colors of lights are put on as decorations. If a normal tree were there, the branches broken off by the wind would create issues when landing or taking off.”

[...]

Hamazura Shiage then jumped out into the night sky.

They were around 20 meters above the heliport. Gravity slammed Hamazura into the tree made of cloth. The yacht sail-like decoration snapped, but it absorbed enough of the shock for Hamazura to avoid receiving a fatal injury when he landed on the heliport.

Toaru Majutsu no Index vol.19