De Guzman, champion in the Manzano Memorial Cup last week, outplayed Borgs Solpico, 6-4, 6-4.
De Castro, a high school freshman at La Salle-Greenhills, defeated Janji Soquino, 6-1, 6-4, to arrange a Final Four duel with Yannick Guba, a 6-2, 6-1 winner over Irwin de Guzman.
Earlier, Arithmetico Lim clobbered Christian Canlas, 6-2, 6-2, and Ed Angelo Diez outclassed Hussein Macapendeg, 6-0, 6-1, to forge a boys’ 14-under semifinal showdown in this event organized by the Children’s Tennis Workshop and supported by Adidas and Sports Kids.
In other matches, Hamza Macapendeg defeated Daniel Macalino, 6-2, 6-0, to advance against Bryan Deo Dayleg, who beat Gerber Mamawal, 6-3, 6-3.
In the girls’ 16-under division, Bernardine Sepulveda downed Angelica Ngo, 6-1, 6-1, to advance to the semifinal round against German Angela Wolff, who survived Melissa Orteza, 6-2, 2-6, 7-5. Other winners were Ivy de Castro and Julie Base.
Semifinalists in the girls’ 12-under class were Bambi Zoleta, Julie Ann Jopia, Julie Em Botor and Jessica Agra.
Gaining semifinal slots in the unisex 10-under were Zoleta, who conquered Sarah Jane Lim, 6-3, 6-3; Gerard Ngo, who struggled past Bernardine Siso, 6-4, 7-6; Patrick Ken Arevalo, who blasted Joseph Baldonado, 6-0, 6-0; and Agra, a 6-4, 6-4 winner over Tomic Apacible.