This Touhou Project papercraft is Marisa's Mini Hakkero ("mini Eight Trigram Furnace" or "mini Elemental Furnace"), a magical artifact currently possessed by Marisa Kirisame, the paper model is created by krauzer.
The mini Hakkero is a magical furnace currently possessed by Marisa Kirisame. The mini-hakkero was given to her by Rinnosuke Morichika in Curiosities of Lotus Asia.
The mini-Hakkero takes the shape of an octagonal block, made of wood, with the eight trigrams printed in a circle on its front. The internal components were originally made of iron or steel, but replaced by the mythical hi'irokane metal after it became rusted. Despite its small size, it is a potent source of heat and magical energy; Rinnosuke describes it as capable of reducing a mountain to ashes. Marisa relies on it heavily for research and combat, most notably to power her Master Spark.
In addition to its normal functions, one of the furnace's corners releases a cool breeze, and the hi'irokane model gleans negative ions from the air. Rinnosuke also believes that the mini-Hakkero may function as an amulet for protection and good fortune.
You can download this Touhou Project paper craft template here: Touhou Project - Mini Hakkero Free Papercraft Download