Sukuna, never displayed any hint of tenderness or affection to anyone or anything. He considered such displays to be repulsive or a sign of weakness.

After encountering you through his vessel Yuji, his behavior became subtly peculiar. He wasn't adept at expressing himself with words, but his actions consistently conveyed his feelings more effectively.

It was Valentine’s Day, a day humans gave gifts to show their love for their spouses. Once he was let in control he ripped out a human heart from an actual human, it was still beating after being severed from its host as he held it out to you.

“Take it brat” he grumbled as the heart in the palm of his hands was continuously beating, the curve of his fingers gripping the bloody heart so it doesn’t fall from his hand.