Something bothers me about this movie....

The reason for this is never fully explained in the movie, but it seems to be a plot device to emphasize Kon’s role as a character with some unique, often overlooked abilities. Kon, being a modified soul with a consciousness separate from the main Soul Society characters, might be outside the direct influence of the memory-erasing event. This could also be linked to his less direct connection to the spiritual power dynamics of the Soul Society, making him immune to the memory alteration that affected others.

Ultimately, Kon’s ability to remember Rukia serves as a narrative tool to help drive the plot forward and allows him to act as a bridge between the world of the living and the events occurring in the Soul Society.