Isekai Maou to Shoukan Shoujo Dorei Majutsu - Volume 2 Chapter 1.08

Riku Aoyama was just a broke, unlucky and starving college dropout waiting for his time and scraping by on instant noodles, and ended up as part-time buddy—until a mysterious vending machine offered him a deal: a system that lets him buy anything.Want a skills? Check.Looking for knowledge? Instantly downloaded.Legendary weapons? Delivered to his door.Authority, time, fate, even the affection of others? All up for sale—if he can pay the price.With the Infinite Wallet System, Riku’s once-pathetic life turns into a wild ride of action, opportunity, and temptation. From unlocking forbidden martial arts to building a harem of powerful women drawn to his rising charisma, Riku is determined to forge an empire, one purchase at a time.But every system has its cost. As he gains power, hidden forces begin to notice his ascent. Gods, demons, and beings beyond reality have started watching—and some want to claim the system for themselves.Action-packed, hilarious, and mature, this is the story of a man who can buy everything—except his own peace of mind.

The scum’s or villain’s long road of transformation was tentatively set to the world:
The abandonment of the educated youth’s wife (Completed)
The hidden marriage of the scum film emperor (Completed)
The best brother in the world (Completed)
The Phoenix male who destroy the bridge after crossing the river (Completed)
The treasonous general (Completed)
I’m an honest man (Completed)
To become the top scorer in the School of Agriculture (Completed)
The soft rice man’s self-cultivation (Completed)
The whole world is reborn (Completed)
I want to survive on a desert island (Completed)
The stallion male who has seized the opportunity (Completed)
The perverted self-salvation (Completed)
The spring of the loafer (Completed)
The misplaced life (Completed)
The miser career (Completed)
The ghost is out of feeling (Completed)
The Queen’s favorite husband (Completed)
The vicious girl with her godfather (Completed)
I want to be a good person (Completed)
I does not tear up the family (Completed)
The perverted common plant (Completed)
The Mary Sue’s men (Completed)
Every time I was reborn, someone wants to kill me (Completed)
The old people’s counterattack path (Completed)
The global evolution (Completed)
When I became a net red (Completed)
For you, good person (Completed)
His heart had white moonlight (Completed)

- Description from Novelupdates

Yun Ran, the successor of Qingfeng View, accidentally got transmigrated into a book due to a blunder.Even more speechlessly, she ended up as a character destined to die early.As the heiress of a wealthy family, not only was her luck and destiny stolen, despised by the heavens, but she was also backstabbed by her own mother, who is the female protagonist, becoming a stepping stone for the male and female leads' happily ever after - absolutely used as a tool.Faced with a disastrous start: No panic, she could simply revert to her old job, setting up a stall for fortune-telling - first three fortunes free, don't miss out as you pass by~Facing injustice and evil: Little ones, take this, descend heavenly thunder! Open the gates of hell! No petty person shall overpower me, all retreat!!!Facing random strikes of heavenly thunder: Hehe, can’t touch me; ancestors, someone is bullying me, come save me~~~Merely running a fortune-telling stall, casually saving people, occasionally undertaking tasks for some hard-earned money, she caused evil cultivators to flee, broke her peers’ defenses, and made wealthy families wary.Everyone heard that Yun Ran had a backing, the Xie family's notorious young master who 'kills people and is short-lived'.Some resentful and envious people kept waiting and waiting, not only did they fail to see Yun Ran meet her demise, nor the young master Xie pass away, but they witnessed Yun Ran amassing boundless merits, firmly sitting on the throne as the number one person in the mystic sect.And that Mr. Xie, unknowingly picked up the habit of making fortune bursts, remarkably living a long life through sheer spending.

The MC entered the body of the An family eldest son, An Ziran, an arrogant 16 years old boy who weighed 78 kg (~171-172 lbs), who only knew how to eat, play and sleep. Seeing his current body, An Ziran decided his first priority was to LOSE WEIGHT!