Harrison, one of five freshmen on eighth-seeded Kentucky's starting lineup, elevated over Caris LeVert, and drained it. He scored all 12 of his points over the last 8:05.
Nik Stauskas missed a heave at the buzzer and the Wildcats (28-10) rushed off the bench and dogpiled Harrison at midcourt.
This will be Kentucky's 16th trip to the Final Four and it marks the first time an all-freshman starting lineup has made it there since the Fab Five took Michigan in 1992.
Kentucky plays Wisconsin Saturday in Texas.
Stauskas led the second-seeded Wolverines (28-9) with 24 points.
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