With Sasuke it was filthy, so Naruto makes them spar until they reek with sweat, to get closer to what he remembers.

With Sasuke it was guarded, so Naruto keeps a barrier of clothing in place, to get closer to what he remembers.

With Sasuke it was bloody, so Naruto drives teeth into his lips, to get closer to what he remembers.

With Sasuke it was dark, so Naruto turns off the lights and takes him from behind, to get closer to what he remembers.

With Sasuke it was silent, so Naruto grips his throat and strangles the aroused pleas, to get closer to what he remembers.

Sai doesn't smell right, feel right, taste right, look right, sound right—

But for one climactic moment, Naruto can forget.