"I Got a Cheat Skill in Another World" centers on Yuuya Tenjou, a high school student who faces relentless bullying and neglect due to his overweight appearance and lack of self-confidence. His life takes a dramatic turn when he discovers a mysterious portal in his late grandfather’s home, leading to another world. In this alternate realm, Yuuya gains access to a unique system that grants him extraordinary abilities, including a "cheat skill" that allows him to acquire and master skills at an accelerated rate. This newfound power transforms his physical appearance, granting him a fit and attractive physique, and significantly enhances his combat and survival capabilities.

As Yuuya explores the other world, he encounters various challenges, including powerful monsters and rival adventurers. His cheat skill enables him to quickly adapt and overcome these obstacles, earning him recognition and respect. Along the way, he forms alliances with other characters, such as skilled warriors and magical beings, who aid him in his journey. The narrative balances action-packed battles with moments of personal growth, as Yuuya gradually builds confidence and learns to navigate the complexities of his dual life between the two worlds.

The story also delves into Yuuya’s interactions with people from his original world, particularly those who once mistreated him. His transformation and newfound abilities lead to shifting dynamics, as former bullies and peers begin to view him in a different light. The manga explores themes of self-improvement, resilience, and the consequences of power, as Yuuya grapples with the responsibilities that come with his abilities and the moral dilemmas of using them.

The world-building incorporates elements of fantasy and RPG mechanics, with detailed systems for skill acquisition, leveling up, and item crafting. The alternate world is richly depicted, featuring diverse landscapes, magical creatures, and intricate societal structures. The narrative maintains a steady pace, blending episodic adventures with an overarching plot that hints at larger mysteries and conflicts yet to be resolved. Yuuya’s journey is marked by both external challenges and internal struggles, making "I Got a Cheat Skill in Another World" a compelling exploration of personal transformation and the allure of extraordinary power.