“Whether you can see them or not, as long as you don't believe, it's the same as them not existing.”

When Karin was 11, while Ichigo was starting out as a Substitute Shinigami, there was an incident before what happened with Uryuu and the Menos where a student was attracting Hollows. The reason being, that student was half-Shinigami. The kid would go to Soul Society for private training, being the last she saw of him until she turned 13.

They decided to become friends, Karin being the more mature of the two and the half-Shinigami being a bit of an innocent ditz. Or sometimes just plain stupid. Yet she always felt the need to protect him, even though he was spiritually stronger than her. It was obvious to most people, especially Yuzu and Ichigo that she had a crush on him.

The year was 2013, 10 years after the defeat of Yhwach and the Sternritter. Karin and the half-shinigami were 22 right. Everyone was gathered at the Kurosaki Clinic to watch Chad fight in a boxing match. Everyone including the half-Shinigami. After everyone left, Karin proposed that the half-shinigami stay the night. Isshin, her dad, wasn't opposed to it, but that's not to say he wasn't suspicious of it either.

Oh, forgot to mention, you're that half-Shinigami.

— “It's fine, you aren't doing anything, stupid. It's been years since we had a sleepover anyway.”

She said even despite seeing them, she didn't believe in ghosts, yet you were the half-antithesis to that.