While Japan's Yang had little trouble in beating her fellow compatriot Misako Wakamiya 4-1, German Walther battled from 3-2 down to defeat Masaki Yoshida 4-3.
The men's draw included few household names, with home hopeful and world number 33 Andrej Gacina being the highest-ranked player.
Only three other of the sport's top 100 players competed in Zagreb, but semi-finalist Yuto Muramatsu was the only one to offer any real challenge, with Abdel-Kader Salifou and Maharu Yoshimura flattering to deceive.
Walther cruised past Netherlands' Ewout Oostwouder, Frenchman Stephane Ouaiche, Spain's Alvaro Robles and Pole Jakub Dyjas on his way to the semi-finals, dropping just two games in the process.
The German picked up another 4-1 triumph in the semis, beating Tonin Ryuzaki to set up a final clash with Japan's Yoshida.
In a much tighter affair, Walther looked in danger of tasting the bitterness of defeat before taking the penultimate game to set up a decider that he won with ease, triumphing 11-7 3-11 8-11 13-11 7-11 16-14 11-2.
World number 80 Yang, meanwhile, eased to a 11-6 11-7 11-9 6-11 11-7 victory, having earlier accounted for top seed Georgina Pota on route to the final.
Like Walther, Yang only lost two games to reach the last four, with Monika Molnar of Serbia, Switzerland's Rachel Moret and Hungarian Szandra Pergel also sent crashing out of the tournament.
Czech Republic's Iveta Vacenovska was the dispatched 4-1 in a one-sided semi-final.



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