Got a great system! Narcissist on the way.

The story is about a boy named Stein Heller who was transmigrated into a body of a boy in another world. After getting kidnapped, some old freaky scientist tried to run experiment on Stein Heller but it failed with an explosion. Yet, Stein got a system and ending up transmigrated his soul in Roy Chester's body. What adventure Stein will have in isekai? What kind of life he will get....!? Read the novel if you interested in thrilling, perverted adventure of Stein Heller in another world! ====================== Let me tell you something, english is not my first language but to share my creation i have to write in english. (I do not own this Cover Pic) So, you may found grammatical errors in the story but I'll try my best to not make any..thank u :) It contains 18+ and a few brutal scenes that's why read on your own risk ( i know kids nowadays like to take risks —_–) (Not a dense mc) (Shameless mc) (Narcissist mc) ( Ruthless mc) [Overall, he's not a righteous guy. Anti-hero mc] Enjoy and motivate me!!