a soft spot

A particular fondness or affection for someone or something, often for reasons that hard to understand or articulate. I've always had a soft spot for cheesy action films—there's just an earnest goofiness about them that I like. Despite how troublesome he could be, the teacher had a soft spot for Daniel.

soft spot

1. A weak or vulnerable point, as in That's the soft spot in his argument. [Mid-1900s]

2. have a soft spot for. Have a tender or sentimental feeling for, as in Grandpa had a soft spot for Brian, his first grandson. This expression, first recorded in 1753 as "a soft place in one's heart," uses soft in the sense of "tender."