The concept of odd elasticity is useful to characterize non-reciprocality in active systems such as micromachines and microswimmers. As an example, we first introduce a model for a thermally driven microswimmer in which three spheres are connected by two springs with odd elasticity. Using Onsager’s variational principle, we derive dynamical equations for a nonequilibrium active system with odd elasticity. We further investigate the emergence of odd elasticity in an elastic microswimmer model by using a reinforcement learning method.