Disclosed is an operating method of an apparatus operated by at least one processor, the operating method including: fusing at least some feature maps generated by layers of a target model performing online continual learning to generate a fused feature map; identifying features with high attention in the fused feature map as shortcut features in a ratio based on a drop intensity; and removing the shortcut features from a target feature map output from a predetermined layer of the target model and input to a next layer.