Using the Core Manual

Kuys nodded his head calmly upon hearing Mario's report. 

Fifteen years ago, a Beast Tide also occurred in the city. 

During that time, the adopted child of Mario also became an adventurer for the sake of the city. 

The two of them were very supportive of the child back then, even helping him register in the adventurer's guild after awakening. Although his 'talent' was not exceptional, all that matters was his spirit for adventuring. 

Unfortunately, before he could mature, he was also killed during the Beast Tide.

That child and Ban have many similarities. That's why the two of them became close to Ban in a short time. 

Of course, what happened was already in the past. They have already moved on from it. Nevertheless, they no longer wanted to repeat what happened back then.