WARNING: The following contains spoilers for Dr. Stone Season 2, Episode 7, "Secret Mission" now streaming on Crunchyroll.
Ever since his introduction in Dr. Stone, Ukyo has proven to be quite the perplexing and interesting character. Debuting as a member of Tsukasa’s upper echelon, Ukyo was believed to have a deep loyalty to the empire. He diverges from this notion when Ukyo lies about how he found Chrome. In retrospect, his other actions have come into question along with his motivation. In Season 2, Episode 7, all is revealed. Much like Senku, Ukyo only wants to protect humanity, and he aligns himself with the Kingdom of Science.
Senku and Gen are continuing their plan to convert members within Tsukasa’s empire over to their side using a Lillian Weinberg impression and a devious lie. Thanks to Nikki's voice coaching, the plan is going a lot smoother. Ukyo catches wind and wants to hear Lillian for himself. His supernatural hearing poses an extreme threat to the overall plan. Ukyo is probably the only person in the entire region who would be able to tell the difference with precision, which is precisely what he does.
Ukyo does make note that normally he would not be able to tell the difference because the impression is stellar, but the lack of vibration in the voice after a fantastic singing demonstration exposed Gen as a fraud. Strangely, he says this in English and Gen catches on to that. Gen recalls that Ukyo never shot to kill and didn't report directly to Tsukasa after discovering Chrome, Magma and himself dropping off the cell phone. Gen also hypothesizes that Ukyo spoke in English so the Japanese-speaking residents would not discover Gen’s secret. The discussion between Senku and Ukyo that follows reveals it was Ukyo who supplied Chrome with the battery for his escape plan.
Ukyo is a high-ranking official under Tsukasa, but clearly has different goals from his boss. Ukyo remembers the pain and sorrow he felt watching Tsukasa murder people; their broken petrified remains haunt him. He also remembers seeing Yuzuriha collecting the shards of the broken stone humans and repairing them, an act of kindness that inspired him and made him want to meet Senku himself.
Now talking with Senku, Ukyo cuts a deal to help the Kingdom of Science under the condition that the Kingdom does not kill anyone. Luckily, Senku didn't want to kill anyone to begin with, so he's able to make a great deal and strip Tsukasa of one of his top men. Ukyo’s impressive hearing skills were a potent resource for Tsukasa, but now this skill can be used to Senku’s benefit. Senku can worry less about details being leaked to Tsukasa through surveillance. More importantly, Tsukasa doesn’t even know he has a double agent against him. Communications are yet again on Senku’s side.
As for Ukyo, his motivations are finally clear and align with Senku’s. Both parties wish to protect humanity and avoid violence if possible. A clearer look into his character reveals why he hesitated to kill Chrome and Magma even though he obviously possessed the skills to do so even in the fog. A fruitful relationship between the two could lead to higher levels of success well beyond Tsukasa if all goes well for them.
The final battle is on. Senku looks to take control of the miracle cave with his tank, the might of the villagers, and his allies. At the end of the episode, Tsukasa discovers the cell phone after Senku is finished with that phase of the plan. That discovery alone could spell trouble for the Kingdom of Science, but Senku’s odds are looking better than ever.