It had been five minutes since they flew. But, nothing had happened. However, Ace felt Red was more nervous as they flew further. He felt the flying skate was warrier and slower as the time passed.
A few times, he wanted to ask Geo to go down. However, he was always hesitant, as he felt nothing was wrong. So, he chose to be silent. Although he didn't know how Red felt the danger, he quite believed her, as he also felt the atmosphere became heavier.
He speculated that what Red felt was a kind of aura or something. This aura was released by a strong monster to warn other monsters that they entered its territory or its sphere of influence.
His mother-in-law also thought the same. She said, such behavior was often done by animals before the Earth was polluted that made them extinct. It was explained in many records.