There, half of the characters can tell Kirito, and some more can be captured on video and prove their words. The same Administrator sometimes speaks in rather transparent hints, but Kirito, besides being dumb, also forgets everything when leaving the world of dreams. But of course, no exposure will happen for some stupid reasons. I wouldn't be surprised if Fujino, for example, thinks that Suguha got too involved in this case, creating a huge hole in the plot, and reduces her time in the game. Liz will obviously fall into Inoda's hands, so her knowledge is worthless. And Sinon, for example, will lose to his rival from the Council in order to finally cut off all the possibilities that Kirito can find out something. Only at the end. I hope all these actions with Suguha and Sinon were not in vain, and Kirito will have the choice to just spit on Asuna's betrayal and stay with them. I would not say that this is a victory for Kirito, but it is quite an adequate ending considering that Kirito is already cheating on Asuna himself. It would be stupid if, with all the events with Suguha and Sinon, Kirito would end up pretending to be a righteous martyr.
P.s There is also Agil who looks out for Kirito, but he probably doesn't care that Asuna is cheating on Kirito, as long as Kirito doesn't die somewhere in his adventures.