The eruption occurred on Mount Fuji 's eastâ `` north-east slope and made three new volcanic openings called No. 1 , No. 2 , and No. 3 HÅ ei vents . The eruption occurred on Mount Fuji 's eastâ `` north-east flank and formed three new volcanic vents , named No. 1 , No. 2 , and No. 3 HÅ ei vents .