Rui had spent a few days at the Orphanage. Spending time with his family and catching up with all of them. He even spent time playfully training Max and Mana for Martial Art. Surprisingly, he found that perhaps their desire to be Martial Artists weren't too outlandish.
Max was quite strong and tough for his age; his muscles were remarkably developed for someone of his age and he clearly spent a lot of time on physically intensive activities. He had potential to be quite remarkable.
Mana on the other hand was remarkably agile and fast. She was remarkably nimble and light on her feet, capable mobile maneuvers.
Frankly, if they underwent rigorous and thorough training, they had a decent chance to eventually crack the Martial Entrance Exam when they were older. Perhaps they wouldn't crack it at the age of thirteen like Rui did, but atleast when they were older, it wasn't unrealistic.