[3][4] Johnson attended Grosse Pointe South High School, playing football as a cornerback, wide receiver and punt returner.

[8] He was one of the first Michigan recruits to benefit from the new rule allowing players to be compensated for the use of their name, image and likeness (NIL).

He finished the 2023 season with the second lowest QB rating when targeted in college football, adding 27 tackles and four interceptions.

[26] Entering his junior season, Johnson was ranked as the best cornerback in college football by members of the media.

[30][31][32] In his first game of the season versus Fresno State, Johnson recorded three tackles and had an 86-yard interception returned for a touchdown to secure a win.

[40][41] On December 11, Johnson declared for the 2025 NFL draft, foregoing the ReliaQuest Bowl and his senior season.

[42] He finished his career at the University of Michigan with a 35-6 team record, two Big Ten championships, All-American honors twice and was a national champion (including being the game’s defensive MVP).

In his three years, Johnson appeared in 32 games, recording 68 tackles, 19 passes defended and nine interceptions (including three returned for touchdowns).