Shadow Reborn

The world's top assassin, Ying, was betrayed and killed in an explosion, but was reincarnated as Jade Quinn, a high - school girl who was constantly bullied. She retained her deadly combat and hacking skills, taught the bullies a lesson, took control of her malicious family, protected her disabled brother, shocked the underground racing world, and piqued the curiosity of a billionaire heir.

Shortmax released it as 21 bite-size episodes mixing revenge, billionaire and second chance, made to watch on a phone in one sitting or a few.

The draw here is the slow build to a payback that lands hard. On top of that: the hidden-wealth reveals and the people who misjudged the lead.

At about 25–46 minutes in total, it's quicker to finish than most full-length series.

Start from episode 1 below; autoplay takes you to the next episode when one ends, and nothing needs a sign-up.