In the summer of 2023, Kacper Kostorz was loaned to FC Den Bosch, where he managed to regain his form by scoring 16 goals and providing six assists in 39 appearances. His impressive performance caught the attention of other Dutch clubs, which led to a subsequent loan move to NAC Breda, a team newly promoted to the Eredivisie. The loan agreement with NAC Breda included an option to purchase Kostorz permanently. However, despite initially being a regular player, his performance has been underwhelming, and he has faced difficulties in securing game time, having played only 427 minutes across 14 matches and scoring just one goal. Consequently, NAC Breda is reportedly not inclined to activate the purchase option.