6 Na2S2O3 + 10 KMnO4 + 2 H2O → 3 K2S2O4 + 6 Na2SO4 + 10 MnO2 + 4 KOH
This is an oxidation-reduction (redox) reaction:
10 MnVII + 30 e- → 10 MnIV (reduction)
6 SII - 24 e- → 6 SVI (oxidation)
6 SII - 6 e- → 6 SIII (oxidation)
KMnO4 is an oxidizing agent, Na2S2O3 is a reducing agent, Na2S2O3 is a reducing agent.