Si Yan once ruthlessly complained about Ultraman Zero: "Can Tartarus defeat him in his strongest form? This is too weak!"
As a result, Zuodi suffered retribution - after an accident, he was reborn as Zero's son.
Si Yan's heart was broken: he just wanted to be a salted fish, and he didn't want to be an Ultraman at all, let alone go to the earth to fight monsters and upgrade.
However, due to a twist of fate, he not only became Ultraman, but also awakened the ability to travel through time and space - he could travel freely between universes, and even travel to the past and future at will.
"Since you can't escape, let's change your thinking!" Si Yan's eyes lit up, and he simply sneaked to the earth to fish, and also went to various Ultraman worlds to check in.
From then on, a certain salty boy embarked on a journey across the universe.
On the other hand, in order to find this troubled son, Zero has been talked about countless times by his father Seven...
Purpose: Check in for sightseeing in various Ultraman worlds