There are patron saints in the world. Their wings are black, similar to angels. The only difference is that angels have white wings and patron saints have black wings.
Most angels are ruthless, and the more advanced the angels are, the more ruthless they are.
Patron saints can be promoted to angels, but very few of them are promoted because promotion requires advanced magic power and the perseverance to abandon love.
When a patron saint falls in love with a person, the final result for that person is: death.