Akinjo grew up in the crime-ridden Las DeltasHousing projects in North Richmond, California. He was raised by his grandmother, Roberta Stevenson, because his mother, Monique Divers, died from leukemia when he was a toddler. When Akinjo was 13 years old, his brother died. Many of his friends were also murdered. His father, who is only 16 years older than him, and his uncle were imprisoned or jailed during his childhood. From a young age, Akinjo aspired to become a basketball player and drew inspiration from Chris Paul. At age 11, he was featured in the East Bay Times, who touted him as a "basketball prodigy." Akinjo played for Salesian College Preparatory in Richmond, California, where he was coached by Bill Mellis. As a freshman, he stood 5'8 but had a growth spurt. At the 2017 MLK Classic, Akinjo scored 29 points in a 45–36 win over St. John Bosco-Bellflower. As a senior, he averaged 20.7 points and 5.2 assists per game, leading his team to a 30–2 record and the CIF North Coast SectionDivision III title.
On November 19, 2018, Akinjo earned his first Big East Conference Freshman of the Week honors after averaging 14.3 points and 4.7 assists per game in three games. He made a three-pointer with 4.9 seconds left in regulation to force overtime in a 76–73 win over South Florida. On December 22, Akinjo scored a career-high 25 points in a 102–94 victory over Arkansas–Little Rock. He matched his career-high on March 9, 2019, scoring 25 points with five three-pointers in an 86–84 win over 16th-ranked Marquette. At the end of the regular season, Akinjo was named Big East Freshman of the Year and was a unanimous pick for the Big East All-Freshman Team. As a freshman, he averaged 13.4 points, 5.2 assists, 2.9 rebounds and 1.1 steals per game. Akinjo made his sophomore debut on November 6, 2019, scoring 20 points, including 17 in the second half, in an 81–68 win over Mount St. Mary's. On December 2, it was announced that Akinjo had left Georgetown and was entering the transfer portal along with several other Georgetown players. In seven games, he averaged 13.4 points, 4.4 assists and three rebounds per game. On January 1, 2020, Akinjo committed to Arizona, where he would become eligible for the second half of his following season, barring a waiver for immediate eligibility.
