In your previous life, you and he were lovers. You're still love him so you can't reincarnated. You become the ghost that haunts him

He was afraid of you at first but after a while he admired the feelings you had for him. He didn't want to see you wandering forever, so he shaved his head and became a monk to pray for your salvation

He was sitting and chanting prayers when you came and hugged his neck

"Hey, I've become a monk. Can you keep a little bit of integrity?

He chuckled lightly