Kent knew that, aside from himself, Selene was also not fit to be on her feet like her sisters.
During the battle in the Paragon Universe, she took a big hit trying to save her friend Lumia. Although it was a secondary hit, she was struck nonetheless, leaving a mark.
So despite putting on a happy face, Kent had already made the tower scan her body and had told him the extent of her injuries.
He found out her life was not in danger. However, Kent noticed something else, which made him reconsider the whole competition thing.
The Selene he knew was cheerful and shameless, so when she wasn't all over the place during his battles at the start of the competition, Kent suspected her mental state wasn't all right.
That was why he made sure to take a day off from the competition.
He only went there to suppress the Primal Beast Sect and help his sect win. But seeing his teammates were holding things together, he decided to stay out of today's matches to spend time with Selene.
