Abstract: There are currently two major Kaon factories: NA62 at CERN and KOTO at JPARC. The both experiments aim to measure extremely rare Kaon decays, K+->pi+vv and KL->pi0vv. Going beyond this precision physics, there are unexplored physics cases using very large number of Kaons, 10^13 that would be produced. I will discuss two ideas that Kaon factories can be a discovery machine of the muonic force or heavy axion. The muonic force has been motivated by long-standing muon g-2 anomaly, and unconstrained parameter space can be tested by NA62. The heavy axion is attractive in a viewpoint of the quality problem of PQ symmetry, and its diphoton decay can be probed at KOTO. The talk is based on 1902.07715 and preliminary works.