Cell of the present had swallowed Future Cell, but he needed time to absorb and fully wield such immense power. So, after the Cell of the main timeline devoured Future Cell, he immediately left the area and chose to hide for a while. He knew that Earth in the main timeline had a powerful expert—Gaino.
Ever since emerging from his incubation chamber, he had constantly observed all the strong fighters on Earth. He knew of Gaino as well. Although Gaino had never made a move, Cell knew that Gaino was the strongest among them all. His body was sending him a warning of danger.
So he hid in the shadows and slowly built up his strength. When he saw Android 17 and Android 18, he had considered swallowing them directly. But he told himself that the time was not yet right. He had to wait for an opportunity—until his strength was enough to contend with Gaino. Only then could he openly appear before Gaino and the others.
However, Future Cell's appearance disrupted his plans, leaving him no choice but to change them. When he saw Future Cell swallow Android 17, an idea came to him. He knew that in a one-on-one fight, he definitely would not be Gaino's match. But if he swallowed his future self, his strength would surely soar, giving him the means to challenge Gaino.
Once he had absorbed all of Future Cell's power, he would be able to challenge Gaino. Cell also thought that it would be perfect if he could swallow Android 18 as well. Only by absorbing both Android 17 and Android 18 could his strength become flawless.
On Gaino's side, after hearing Goku's account, Gaino said, "So there were two Cells, but one of them swallowed the other. Is that right?"
"Yes, yes,