An elementary school homeroom teacher in Kanagawa Prefecture on Friday was forced to leave an ALT alone with a class for five minutes instantly causing the students to become insanely irrational.
Police and the fire brigade arrived shortly after the mass student riot broke out.
The incident resulted in two fatalities and seven serious injuries, with the mayhem quickly spreading to neighbouring classrooms.
Local residents witnessed children running frantically around the schoolyard, with many students stripping their clothes off and covering their skin with tribal-style body paintings.
The school has been temporarily closed and students are currently receiving counselling.