[Crossover] How I, the Villain, Saved the World

To-read list: The Gojo and Zenin Families Are Still Doing Cross-Server Gigs Today [This story is also known as We Sit Beside a Great Heap of Bones and Listen to Miss Mori's Tales of Her Past Scumbaggery] My name is Mori Nao, and I'm from Yokohama. I'm still just an ordinary college student, but if I kill my dad, I can immediately inherit a multinational company that owns five office buildings. But I won't, because I'm a good person. One day, my senior, nicknamed Good-for-Nothing Tsuna, told me that my black-hearted marshmallow of a chuunibyou cousin had decided to take over the world. The solution was to gather seven Guardians, including me, and have him fight them one-on-one in seven consecutive matches. I don't really get why we couldn't just gang up on him, but I accepted the job. Want to know why? Because I'm a good person. I firmly carried on my senior's legacy (crossed out), made a three-month wager with my cousin, and got ready to beat him to a pulp when the time was up. After all, how hard could it be to round up seven measly Guardians? With all the connections I'd made wandering around the world, it should be a piece of cake, right? Full of confidence, I set off to find the Guardians. Full of confidence, I offered them their rings. Full of confidence, I listened as my friends and family roasted me for my scummy past... Wait, hold on. Why have we suddenly started reminiscing about the terrible things I did when I was young and stupid? I haven't been a villain in years! I've become a good person! * Mori Nao figured that someone like her, who'd learned nothing but nasty personalities and dirty tricks, and who'd always resorted to rough and reckless methods to do bad things as a teenager, was bound to grow up into a villain. But someone always stepped in to stop her, guide her, accept her, and stumble along beside her as she grew. Under the circumstances, was it really such a big deal for a dignified villain to be chosen as the savior who would save the world? To repay all that precious affection, Mori Nao worked very hard to turn over a new leaf... evolving from [Grade-A Scumbag] to [Slightly Scummy] (doge). Reading guide: 1. [All-around wish-fulfillment story, with everyone having a one-sided crush on the heroine. Mainly friendship, with subtle romance.] 2. [An old-school, chaotic crossover. Flashbacks are told out of order. It passed review, but the writing is a little rough.] 3. (The blurb has been saved as a screenshot.) 4. The glory belongs to the original works. Any out-of-character writing is on me. Theme: Learn to be sincere over the course of a lifetime