Gerupa' was a past lizardman hero of the Blue Tailed Tribe.
Thirty years ago, a Nekoya Door first appeared before the Blue Tailed Tribe. Gerupa was the one that entered the door and discovered the Western Restaurant Nekoya. He brought back the dish Omelette Rice back to his tribe and since them every Day of Satur has been a festival for his tribe in which one of their strongest warriors would be granted permission to enter the Door and bring back the wondrous Other World food.
Isekai Shokudou Episode 4