When the Mother Goddess fell, her brothers all changed. When the seventh brother mentioned that there was a way to bring her back, but that it required one life in exchange for another, all nine brothers were willing to give up their own lives, as long as the method could save their mother. They would do anything...
But in the end, they discovered that their lives could not be exchanged for hers. Only their little sister's could...
Some of the brothers chose to back out. They refused to let this method take their little sister from them!
But in the end, they still lost their lively, cheerful, quirky little sister...
They regretted what they had done. They hadn't stepped forward or offered help. They had simply stood there like fools, watching her body fade away...
(Not too angsty, but proceed with caution if you don't like that kind of thing!)
The male lead doesn't get much screen time, but he's deeply devoted. If that's not your thing, you may want to steer clear!