2 KMnO4 + 8 KNO2 + 3 H2SO4 → K2SO + 2 MnSO4 + 8 KNO3 + 3 H2O
This is an oxidation-reduction (redox) reaction:
2 MnVII + 10 e- → 2 MnII (reduction)
SVI + 6 e- → S0 (reduction)
8 NIII - 16 e- → 8 NV (oxidation)
KMnO4 is an oxidizing agent, H2SO4 is an oxidizing agent, KNO2 is a reducing agent.