It depends on whether it is a corporate-type DC or an individual-type DC (iDeCo).
<Corporate-type DC>
The company (*1) pays contributions.
Some DC plans may require participants to make contributions (paid from their salary).
(*1) If stipulated in the plan document, participants are allowed to make contributions on top of the company contributions (plan sponsor contributions). (employee matching contribution/participant contributions)
<Individual-type DC (iDeCo)>
The participant (*2) pays contributions.
(*2) Companies who meet the legal requirements can make contributions on top of the contributions made by participants by notifying the National Pension Fund Association. (iDeCo Plus)