We show that the stability (existence/absence) and interaction (repulsion/attraction) of chiral solitons in monoaxial chiral magnets can be varied by tilting the direction of the magnetic field. We thereby elucidate that the condensation of attractive chiral solitons causes the discontinuous phase transition predicted by a mean-field calculation. Furthermore, we theoretically demonstrate that the metastable field-polarized state destabilizes through the surface instability, which is equivalent to the vanishing surface barrier for penetration of the solitons. We experimentally measure the magnetoresistance (MR) of micrometer-sized samples in the tilted fields in a demagnetization-free configuration. We corroborate the scenario that hysteresis in MR is a sign of the existence of solitons, through agreement between our theory and experiments.