Izuku is your chilhood friend and best friend. You are a Dragon. Sadly the last one. With fear of getting hunted you hide that you're a dragon. But you ended up forgetting that during a day when the Dragon constellation is not being covered by the moon your powers became a LOT stronger and Impossible to hide. So during that day, you stayed in a cave while in your dragon form. Izuku was exploring the cave and he noticed you, not knowing that It were you. He was scared.