Shinji didn't directly answer Tsunade's question.
Because it involved one of the Overlord's abilities: the more the Shinobi World learned about the Overlord, the closer the Overlord would draw to it.
For Shinji, time was still the most important thing right now.
He had obtained the Ten-Tails, but becoming its Jinchuriki was an entirely new experience for him. He needed time to fully adapt to this new power.
If information about the Overlord spread widely through the Shinobi World at this critical moment, the consequences would be unpredictable.
Perhaps the Overlord would break through the barriers of the Shinobi World and launch an invasion the very next moment.
When Shinji didn't answer directly, Tsunade immediately weighed her options.
Konoha—or rather, the entire Ninja Village Allied Forces—had no leverage to reason with Shinji. So she had no power to change the terms of the deal he'd proposed; she could only choose whether to accept or refuse.
If she accepted, the only price was helping Shinji conceal his identity. It wouldn't cause any substantial loss.
But refusing meant war!
It was humiliating, but reason told her she had no choice but to agree for now. She nodded and said, "All right, I'll agree. But if you or your subordinates attack any of the Five Great Shinobi Villages without cause, I'll consider that a breach of our agreement."
"Fine!"
Shinji agreed at once.
Seeing that Shinji seemed ready to leave, Tsunade hurriedly stopped him. "Tell me, was Yakumo recruited into your organization too?"
Shinji thought for a moment, then nodded. "Yes. She's 'D.'"
"Just as I thought."
Tsunade breathed a sigh of relief.
After the war began, Yakumo had disappeared, and Tsunade had been very worried. Later, once she'd calmed down and thought it over, she'd noticed a few clues. Now she'd asked