The male and female protagonists eventually reincarnated as women, but they did not become humans at the same time, causing the female protagonist to be very sad and transform into Meng Po. Do you have any books that you recommend?

No one knows? It started with a chance encounter between the male and female leads. The female lead told the male lead a fake name, and the male lead married a woman with the same name. It was only on their wedding night that they found out that it was not the female lead but someone else. Then, they seemed to have a few reincarnations, and in one of them, the female lead became a tree.

Answer 1

I don't think it'll necessarily meet your needs, but I'll try my best to recommend a novel that's most relevant to your description. The Love of the Three Realms with Meng Po is a Xianxia novel written by the author, Yi Dong Chun Qiu. The general plot of this novel is:

They met each other in the Ghost Realm, fell in love in the Human Realm, broke off their relationship in the Immortal Realm, and forgot each other. In the end, he chose the name she gave him and stayed with her for the rest of his life.
----------------------------
The book,"The Love of the Two Worlds", was a fantasy romance novel written by the author, a fairy. The general plot of this novel was:

An ancient woman had transmigrated to the modern world, a world where supernatural powers ruled the world. She fell in love with someone she shouldn't have liked. The right person had already appeared. Should she resign herself to fate and marry the one who was willing to be fated, or should she defy fate and change her fate to marry the one who would never abandon her? He had tortured a little girl from another world who had transmigrated to ancient times, a person who had once been loved by thousands of people, transmigrated to an extremely unloved concubine's daughter, and had to marry a sickly prince who had been plagued by illness since he was young and would not live for many days? I'm here to enjoy my freedom, not to be tortured…A woman disguised as a man to escape from a marriage and was actually caught. Helpless, her husband was actually him from her previous life…Wei Tian wrote two stories in one article. The two female leads were forced to exchange identities. One was free to do whatever she wanted in ancient times, trying to dominate the dynasty and obtain everything…The other was filled with despair in modern times, but she was reborn. Since the heavens treated her so well, she would be arrogant for once and defy the heavens for once!
----------------------------
"Meng Po's Lord Nether King" was a modern romance novel written by the author, Song of Long Goodbye. The general plot of this novel was:

I am Meng Po. I provide Meng Po soup to all the reincarnated spirit bodies by the Bridge of Helplessness to erase their memories of their previous lives.
He is the King of Hell. He asked me to go to the human world to find a man who escaped Meng Po's soup.
But that person was just a clone of him…
----------------------------
"Three Lifetimes of Sadomasochism" was a fantasy romance novel written by the author Udumbara. The general plot of this novel was:

She had been a demon for her entire life and had been destroyed by the heavens. He had defied the heavens and changed her fate to save her. She had become a king for the second time and died for power. He had sealed his body and waited for her for a thousand years. She had been a concubine for three lifetimes and died for love. He had abandoned the world and entered hell together. Three lifetimes, never give up. If I love you, even if I go to hell, what do I have to fear? With a single thought, I became a demon and a human, but I became a ghost and a god for you. Three lifetimes of entanglement, love and hate, born in different nests, but died in the same cave! Palace strife, politics, war, the underworld, all for you!
----------------------------
"Meng Po Lai Wan Tang" was a light novel written by the author, Ye Qianmi. The general plot of this novel was:

Many people probably yearned to be reborn, but after dying and coming back to life with memories, Jiang Qin was extremely exhausted. Memories were too heavy. Regardless of whether they were loved or hated, they could not retain anything.
The female protagonist had no system or ability. She was just an ordinary modern girl who was not very smart.
[First Life: The Self-Salvation of the Vicious Supporting Female Lead (The first story was born out of a novel I read, I can't remember the name)]
Second life: Xunyang Liang's death. Third life: The Dignity of the Fujin Kingdom of the Qing Dynasty. Fourth life: The First Goddess of War of Ten Miles of Peach Blossom. Planning for ten lifetimes, sometimes there was a CP, sometimes there wasn't.
----------------------------
"Crossing the Path to Riches of a Virtuous Woman's Favorite Husband" was an ancient romance novel written by a dead immortal. The general plot of this novel was:

It was a one-on-one battle with the female venerable dynasty. The female protagonist, Wen Hao, was an inspirational businessman in the 21st century. She had died of old age. After arriving in the netherworld, he made outstanding contributions and perfectly realized the mechanized production of Meng Po Soup. He solved the problem of the netherworld being full of ghosts and the difficulty of ordinary ghosts to be reincarnated. Later, her best friends also came to meet up. Because of a mechanical malfunction, the Meng Po soup that the two drank was mixed with water, and they were reincarnated into the Female Venerable Dynasty with the memories of their previous lives. He was really poor. A person in a remote village could have 800 tricks up his sleeve. It was true that he had many tricks up his sleeve, but the warmth of helping each other was also true. They didn't have any family or relatives that were too extreme, but everyone had their own selfish motives… Under Wen Hao's guidance, everyone was able to live their ideal lives step by step… The male protagonist had appeared in the female protagonist's house from the beginning. He was an inevitable tragic figure in the female protagonist's dynasty. It could be said that he was crippled. Later, he was saved step by step by the female protagonist in the days they spent together…
----------------------------
"The Princess 'Love Across Thousands of Years" was an ancient romance novel written by the late author, Spark. The general plot of this novel was:

She was Meng Xin, a little woman who was doted on by her husband in the 21st century. After experiencing illness, death, and rebirth, she gradually became independent and powerful.
When she first came to a foreign continent, she had parents who doted on her and four brothers who doted on her.
His eldest brother, Meng Kai, was respectfully addressed by the world as "Young Master Xiao". His second brother, Meng Xu, was known as the "Master of the Art Saint". His third brother, Meng Kun, was known as the "Benevolent Young Master". His fourth brother, Meng Yu, was called "Young Master Ghosthand" by the world.
On the same day, Meng Xin saved the four of them and became her best partner in building her own mysterious power.
Five years later, Meng Xin found out that her previous husband, Li Xiang, had reincarnated into this continent. After a few twists and turns and experiencing the trials of life and death, Li Xiang, who was also the reincarnated Fang Xiang, finally received the recognition of the Meng family.
After experiencing her first life and death experience in the other world, she knew that she and Fang Xiang were the reincarnation of Princess Xin and King Xiang of the Ghost Realm from a thousand years ago. She also knew that they had the responsibility of subduing demons and devils.
When they got rid of the Demon King, they found out that they were the reincarnations of Goddess Mengyao and General Batian, who had self-destructed and died together with the Demon King ten thousand years ago.
What awaited them next was the upcoming Great War of Gods and Demons.
----------------------------
"Rebirth, Unstable Life" was a modern romance novel written by the author, Broken Dreams, Unrealisation. The general plot of this novel was:

Yi Huan had been missing a soul and a spirit since she was a child. She was in a daze. Every time the Gate of Hell opened on the 15th day of the seventh month, she had to enter the Bridge of Helplessness in Hell. When she was six years old, her soul left her body again and came to the Bridge of Helplessness. Meng Po took pity on her and put the Soul Gathering Pearl into her Sea of Consciousness. She did not expect that her soul and spirit had already made up for the other two souls and six spirits. Moreover, she was harmed by evil people. She was about to reincarnate with resentment and hostility. When she passed by the Bridge of Helplessness, she was sucked into the female protagonist's body by the Soul Gathering Pearl. From then on, the female protagonist had a two-faced personality…and also started her own ups and downs in life!
----------------------------
"The Reborn Daughter's Supporting System Is Too Calm" was a fantasy romance novel written by the author, Starry Misty Rain. The general plot of this novel was:

Male protagonist:
In the first year she left, he had hoped that as long as you came back, he would not let you suffer any more grievances.
In the sixth year after she left, he said in despair,"If anyone can find her, I'll give this huge fortune to them."
Twelve years after she disappeared, he had someone forge a strong chain for her when he woke up in the middle of the night.
Eighteen years after she disappeared, the apocalypse arrived and he…went crazy.
Ling Yi, don't let me find you again.
Female Lead Editor:
When she found out that she had suffered all her life because she was a vicious supporting actress, she wanted to cry, but she realized that she had long lost the ability to cry.
An opportunity…
When everything started again, she had become a part of the system. How would her life change? 1v1, Double Clean.
----------------------------
"It's Not Easy to Fall in Love with the King of Hell" was a fantasy romance novel written by the author Bing Xin Yi Dian Yu. The general plot of this novel was:

What kind of chemical reaction would happen between a proud phoenix and a drop of tear that Nüwa shed to mend the sky? Do you know if the Black and White Ghosts are brothers or sisters? Is the Meng Po you saw really her original appearance? The plot was reversed, and then reversed again. Guess the ending!