Although Yu Ying was an extremely powerful figure compared to the vast majority of Outer Realm Cultivators, he was far weaker than Ling Tian and Little Snitch. More importantly, Ling Tian and the others excelled at fighting outnumbered, so aside from providing some information, Yu Ying couldn't be of much help. Once Ling Tian had taken control of Saint Tiger Sect, he wouldn't even need Yu Ying to provide information; after all, Yu Ying hadn't returned to the Outer Realm for hundreds of millions of years and knew little about what was happening there.
Of course, if Yu Ying were the only one left in the Yu Family, Ling Tian would naturally take him along. But now that they knew some members of the Yu Family had survived, helping them grow and rebuild the family became important to Yu Ying. Under the circumstances, it wasn't suitable for Ling Tian to take him along. Their search for Saint-grade Heavenly Treasures would surely be fraught with danger. Even they might run into trouble, let alone Yu Ying. Having him split off with his family was undoubtedly the best choice, and at the very least it would leave Ling Tian with fewer worries and fewer people to fret over.
Yu Ying knew that plenty of people would set their sights on him, since he was a cultivator who had come out of the Demon God restricted zone. But if he kept a low profile and went into hiding, and Ling Tian and Little Snitch occasionally made a show of themselves, no one would bother attacking him.
"That's right. We'll make our move at Saint Tiger Sect next, so every cultivator will know that you're with us, Yu Ying. As long as you keep out of sight while we make our presence known from