Shisui doesn't have to mention his worries about Ashiko's authenticity. Itachi can hear them loudly in his own mind, and he knows how Shisui thinks. He knows what he would be worried about if their situations were reversed, but he's almost certain the odd friendship he had with Ashiko was real. She warned him off and allowed herself to be vulnerable around him. He can't imagine her doing that if there weren't something real there.

As soon as Shisui speaks his last words, Itachi opens his mouth to object 'nothing' before his entire face goes red. There had been drunkeness and a lack of clothing, so can he really say that with impunity? Whatever he says now, he's blushing hard enough Shisui probably won't believe him, but Itachi tries to compose himself anyway.

"I told you, we've been running into each other for several year, and yes we only talked." Now that last bit is a lie.

"I taught her to swim," Itachi adds a little helplessly. There's nothing wrong with that, right? And she braided his hair.