Not in Vain is a captivating Chinese web novel that tells the heartwarming tale of a little mermaid who sacrifices herself in marriage to repay a debt of gratitude. The novel follows the intriguing relationship between Lu Ji, a cold and stern general bound to a wheelchair but destined for recovery, and Yu Xiaoman, his beautiful wife who is revealed to be a mermaid. With themes of drama, fantasy, historical elements, mature content, romance, slice of life, and yaoi, Not in Vain explores the depths of love, sacrifice, and the complexities of human-nonhuman relationships. Adapted to drama CD and manhua, this novel promises a unique blend of emotions and character growth that will keep readers hooked from beginning to end.