Tobi_444
He needs a way to explain the jutsus? How about saying that someone who looks like they’re in anbu, with muted emotions, has been leaving scrolls for you? Good luck trying to find the truth there. Hiruzen doesn’t 100% trust Danzo (Danzo literally tried to assassinate Hiruzen and he wasn’t even surprised), so even if Danzo denied it, he wouldn’t accept the answer. Could someone from Root have decided to pass on secret jutsu to a young talented kid because he wants to strengthen the village? Or are they gifts from someone who was kidnapped into Root, and even though they went through the emotional conditioning process, they still want to help their old friend survive? Maybe they’re worried the MC will also get kidnapped into Root? It’s all about weaving a possible narrative. They’ll take it and run with it.
Worrying about that little detail is unnecessary. You just have to develop bont of camaraderie to high level individuals and get their unconditional support or vouch of approval once you've defeated a Kage powerhouse. Either by design of interconnected trap to appear you've barely won the battle, or by obscuring the result by fighting a Kage powerhouse in privacy, allowing you to fabricate a harrowing result, but he'd have to sacrifice his health in order to appear genuine.