UST Growling Tigers Arana then joined the
UST Growling Tigers. He thought that his basketball career in the major college leagues was over and considered going back home to his province. The following game, he had a career-high 25 points on 9-of-12 shooting, but they still lost to the
Benilde Blazers. He was able to lead Arellano to an upset win over the
Lyceum Pirates with 24 points on 9-of-14 shooting, with 11 rebounds and three blocks. As a result, he was awarded Player of the Week. In a loss to the
San Beda Red Lions, he led the team with 23 points, 15 rebounds, and four blocks. Arellano then got a win over the Altas, in which he contributed 17 points, seven rebounds, and two blocks. They got their fourth win of the season over Benilde, in which he had 13 points, 10 rebounds, and five blocks before fouling out. That would be their last win, as they finished with a record of 4–14 in last place. He was awarded as the NCAA's Rookie of the Year along with a All-Defensive Team selection with averages of 13.4 points, 7.8 rebounds, 2.8 blocks, and 1.4 assists. He also played in the NCAA's All-Star Game, leading the losing team with 22 points and seven rebounds.
NCAA Season 97: Final season Arana was set to return for one more year for
Season 96, turning down the opportunity to join the PBA Draft. However, basketball was not part of Season 96's calendar due to
COVID-19 protocols and his eligibility was transferred to the next season. He received interest from
B.League teams during this time. He was initially diagnosed with a partial ACL tear and ruled out for the season. However, after getting another diagnosis, his ligament was revealed to still be intact, allowing him to return to playing. He made his return in a loss to Benilde, putting up 14 points, 11 rebounds, two assists, and three blocks in limited minutes. In a loss to UPHSD, he had 14 points, 12 rebounds, a steal, and two blocks. Arellano finally ended its losing streak with him leading the way with 17 points, 15 rebounds, three assists, and three blocks. Halfway through the eliminations, he averaged 15.3 points, 13.3 rebounds (tied for first in the league), and a league-leading 3.8 blocks per game, making a case as the league's MVP. In a loss to Lyceum, Arana had a double-double performance of 17 points and 24 rebounds, adding to four blocks, an assist, and a steal, in a losing effort. In a crucial win over the
EAC Generals, he put up 21 points and 18 rebounds to go along with three assists and three blocks. He then collected a career-high 29 rebounds alongside 18 points and two blocks while playing all 40 minutes and made two clutch free throws in a win over the
JRU Heavy Bombers that secured them a spot in the play-in game. His 29 rebounds were just one short of the record for most rebounds grabbed in a single NCAA game, which was set in 2015 by Allwell Oraeme. In the play-in game, the Chiefs were defeated by the Altas and their hopes for making the Final Four were ended. With their early exit, he was no longer in contention for MVP, as they were only awarded to those who led their team to the Final Four. He was still able to win Defensive Player of the Year, and claimed spots on the NCAA's Mythical and All-Defensive Teams. In his final season, he averaged 14.8 points, 17.1 rebounds, and 2.8 blocks in nine games. He then declared for the
2022 PBA draft, ending speculations that he would join a B.League team. ==Professional career==