Don Bosco, unbeaten since their return three years ago in the tournament, tasted defeat at the hands of the Johnden Hortelano-coached SHS-J Eagles.
Ed Macasling single-handedly buoyed the Eagles to the top of the leaderboard and relegating DBC to the cellar.
Macasling scored eight of his team's 14-points in the third quarter as he led SHS-J's defensive formation to limit DBC to a woeful four-point output in the third quarter.
Also under bracket A with SHS-J are University of San Carlos, University of Cebu and Cebu Institute of Technology.
On the other hand, UC scored a blowout victory against USC North Campus A, 100-34.
The victory is making Joever Samonte looking forward to the next battle after debuting in the Milo BEST as coach with a win.
Pierce headed UC's scoring rampage with 20 points while Alviva and Codilla added 12 markers apiece.
The scores
SHS-J (60)-Macasling 13, Roma 11, Cimafranca 6, Gabuya 5, Espina 5, Tagaloguin 4, Gabuya 4, Wong 2, Villarias 2, Uy 2, Seno 2.
DBC (55)- Balorio 9, Tan 9, Ruiz 9, Reroma 6, Belangel 8, Perez 7, Riuz 2, Parcon 2, Becinña 2, Ruiz 2.